Android battery and memory optimizations – Google I/O 2016

Android battery and memory optimizations – Google I/O 2016


ASHISH SHARMA: Welcome. And thank you for coming. And first of all, I want
to thank everyone of you to have waited patiently
outside and in the line. I know it’s really hot. So thank you for that. My name is Ashish Sharma. And I’m the tech lead of the
Volta team inside Android. And we focus on
making the battery lives of Android devices great. And I’m joined with
my colleague Meghan. MEGHAN DESAI: Hi, everyone. My name is Meghan Desai. I’m a product manager on
the Android framework team, working on battery life
and memory optimizations. ASHISH SHARMA: So
today, we’re going to talk about two key
resources on any mobile device that, when running
low, can severely impact the way users use their
phones, battery and memory. We’re going to look
at some optimization techniques and some platform
features, some APIs and battery diagnostic tools to take
away the pain from diagnosing battery problems. Because we know it’s
a non-trivial problem. Battery life, or
extended battery life, is one at the top requested
features on mobile devices today. The phones in our pockets are
more powerful and more capable than any time before us. And there are
hundreds and thousands of applications that keep
us informed and entertained throughout the day. But if there is one thing
that all of us wish we had, it’s a phone whose
battery doesn’t die at the end of the day. Now, how many here
in the audience are worried that their
phones will not last through the end of the day? All right. Almost everyone. And to speak for
the same fact, we’ve seen that on the
Play Store there are hundreds, if not
more, of battery apps that claim to help extend battery
life of mobile devices, and some with as many as 100
million downloads or more. So clearly, it’s a problem
that our users face. We care about. And we in the Volta
team in Android are very passionate
about making it awesome. So let’s start looking
at where does the power on our mobile phones go? Turns out, when
the screen is on, it dominates the power
consumption on your phone more than anything else. When you have your screen on,
you’re either playing a game, or watching a video, or maybe
you’re surfing the internet. And screen turns out to be
a very expensive component on the device, which is
many orders of magnitude more, in terms of
power consumption, than most components
on the device. But our phones also spend a
lot of the time in our pockets when the screen’s
off, like right now. I hope it is. So when the screen is
off and the user is not actively engaged or
interacting with the device, the power consumption
now starts getting dominated by the CPU and
the networking radios. So it might be an application
holding a Wakelock to do some activity. Or there might be a background
job, or a background sync, trying to access
the internet to sync some data in the background. And all of that costs power. So when it comes to optimizing
for power when the screen is off, we want you to think about
three main design principles, Reduce, Defer, and Coalesce
any and all background activity that you can. Now, what do I mean by this? Reducing the background activity
for an app when the user is not actively engaged, or is not
actively using the device, is something that only
application developers that only you can do. You know the logic of
your applications best. You know the constraints
that you’re operating in. And you also know
what your users want from the application. But it’s really,
really important that we try and stay
away from that urge, from that temptation, to
push data onto our devices and keep them fresh even
when the user is not actively using the app. All of you raised
your hands when I asked you if you thought
battery was important. And our users are just like us. So we really want you to think
about reducing any background activity that is possible
that you can help. For activity that you
cannot completely eliminate, and there’s going to be
some cases like that, we want you to really think
hard about deferring it until the time when the
device is on charger. Because the moment the
device is plugged in, any activity that you do
essentially becomes free. And the user does not incur
any battery cost for it. And finally, we
realize, and we know, that there is going to be
cases where you cannot get rid of them completely. You cannot defer them until
the device gets on the charger. So for those, we
want you to start using the JobScheduler API. Because that is an API
that lets Android batch and coalesce a lot of
the background activity, not just from your applications,
but from other applications as well, in order to make
the most efficient use of the CPU and the background
networking traffic. Now, this is really important. I want to spend a minute here. Every time your device
wakes up from suspend, or it activates the mobile
radio to do any networking connectivity, be it for a very
small amount of data packet, there is a fixed cost that
needs to get incurred. Your device goes into
this high power state. And there is going to be a
fixed overhead every time you wake up the device. So there’s an access cost. Now, the more applications
can batch together any of their background
activity and coalesce them, the more efficient
the system becomes. And power on the device can
be really, really reduced. Now, there are some
features in the platform, in the Android operating
system, that automatically help you do a lot of
this Defer and Coalesce in your applications. MEGHAN DESAI: Yeah,
that’s right, Ashish. Let’s start by reviewing
a couple of features we launched with the Marshmallow
release, Doze and App Standby. Say you leave your
phone on the nightstand overnight without
plugging it in. And you wake up in the
morning and your phone’s dead. You’re going to have a bad day. But what Doze tries to do is
coalesce a lot of that power [INAUDIBLE] background
activity that Ashish just talked about so that when you
do wake up in the morning, and you’ve left this
device unused overnight, it’s not draining your battery. And you have some juice
left to go on with your day. So let’s take a look
at how Doze works. Let’s suppose these orange
bars that you’re seeing are some kind of
background activity. And at some point, as I said,
you put this device down. It’s stationary. So it’s sitting on
your nightstand. It’s on battery. It’s not plugged in. And the screen’s off. And the way we tell
that it’s stationary is we use a significant
motion detector on the device. So that’s required for Doze. And at some point, we realize,
oh, the device actually has been stationary
for quite some time. At that point, we actually do
a finer motion detection, just to make sure the device is not
in a steadily moving vehicle. We want to make sure
that it’s stationary with respect to Earth
as the reference point. OK. If this happens, at that
point, the first phase of Doze kicks in. And this stays there for an
order of tens of minutes. At this point, applications
lose Wakelocks, Network Access, and there are no more
GPS or Wi-Fi scans. And their Jobs and
Syncs and Alarms get deferred until the
next maintenance window. So maintenance window is where
all that background activity gets coalesced to. This is where all
these restrictions are lifted for a brief period
of time for applications to be able to perform any kind
of pending background activity to refresh the content. So what we’re
really trying to do is balance battery life
with the expectation of constant freshness that
users have on their devices. Now, the device continues
to be stationary, on battery with the
screen off, then, we can see this repeated pattern,
where the Doze windows are growing exponentially with
maintenance windows in between. And this will continue until
the Doze time, the green bars, get to about a few hours. So that’s Doze in the
Marshmallow release. Now, we also wanted to
improve the power consumption of applications that you haven’t
used over a period of time. And so to optimize that,
we launched App Standby. Let’s keep going. Apps that are unused
after some period of time get considered to be on standby. So usage, in this case,
means applications that have had a foreground
service, some kind of an activity or process,
they have had a notification on the lock screen
that you’ve seen, or the app is explicitly
launched by the user. And if this hasn’t happened
over a period of time, then that application
loses network access. And its jobs and
syncs are deferred while the device is on battery. So they’re deferred to when
you plug in the device. But once you plug in the device,
if the application is still not used, then it will still
be considered standby. And the next time you
unplug the device, it will still, again,
lose network access, and its jobs and syncs will
be deferred to the next time the device gets plugged in. ASHISH SHARMA: Wait, Meghan. So you’re saying if I have
an instant messaging app, and I don’t receive a
message for a long time, and it goes in app
standby, then I might miss the incoming
instant messages or video calls because the app
is in App Standby? MEGHAN DESAI: No, no. Your instant messages are
going to make it through. So for that use case, we, as
part of Doze and App Standby, we launched something called
a high-priority Google Cloud Messaging message, which
now is Firebase Cloud Messaging, if you saw
the announcements today. So this high-priority
message, it’s a push message that
grants the application temporary wakelock and
network access, independent of the device’s Doze state,
or if the app happens to be in App Standby. And this allows the application
to react to the message and put up whatever immediate
notification it needs to put up to the user, whether
it’s an instant message, or an incoming call. Normal Firebase Cloud
Messaging messages during Doze gets batched to the
maintenance windows. So for devices that don’t
have Google Play services, this is where Google
Cloud Messaging lives, or Firebase Cloud
Messaging lives, for devices that don’t have
Google Play services, we actually ship Doze and
App Standby disabled, by default in AOSP. And we instruct our
device vendors in markets where Google Play
Services is not available to work
with their ecosystems to identify an alternate
cloud push messaging service. So we don’t have them
enable Doze and App Standby unless they have
Google Play services, or some alternate cloud-based
push messaging service. ASHISH SHARMA: So,
Meghan, that takes care of my instant messaging
and my video calling apps. But what about the
other use case? I often listen to
music on my device when it’s just lying at home
and the music is playing off of my Bluetooth speakers. Does that mean that when
the device goes indoors my music stops playing? MEGHAN DESAI: No, no. We’ve got you covered
there, as well. We’re going to make sure your
music keeps playing, Ashish. So for that use
case, we actually exempt foreground services
from Doze and App Standby. Often, when you’re
playing music, music applications
rely on what’s called a foreground service. This is a service that has to
have a persistent notification. And such a service is going
to be exempt from Doze and App Standby. So even though your
device will enter Doze, this service will retain its
network access and wakelock access. So it can still
play Ashish’s music. ASHISH SHARMA:
All right, thanks. MEGHAN DESAI: I also said
that alarms get deferred. Now, there are some use cases
where alarms are important, part of what the
application needs to do on behalf of the user. So for those kinds
of use cases, we launched new alarm APIs that
will trigger in a limited way during Doze. And then, finally, for use cases
that cannot be accomplished by Doze and App Standby, we have
a Whitelist on the system that users can add applications to
that will cause the application to be exempt from
Doze and App Standby. Applications can also
prompt users at runtime to be added to this
Whitelist, but this is only for very specific, narrow,
acceptable use cases that you can read about
on our developer site. And doing so would trigger
a Play Store review before your application gets
published to the Play Store. ASHISH SHARMA: So all
this sounds great, Meghan. The features make a
lot of intuitive sense. Doze and App Standby for
cases when my device is not being used, or when I’m
not using my applications. How did we do? Do we have any numbers? MEGHAN DESAI: I think we do. I think we have some numbers. ASHISH SHARMA: Oh, great. So last year, when we
announced Marshmallow, we saw that Doze and App
Standby combined together can increase the standby
battery life of a Nexus 9 tablet almost twice. And so the battery life
almost doubled there. And we also saw up to
30% average improvement in the screen-off battery
life of Nexus 6 devices. There are in a control
group population of Googlers that we have. So clearly, Doze and App Standby
are very important features. And these principles
do seem to work. But I’m still thinking
about one thing. These cases make sense when I’m
not using my device or the apps that I’m not using. But what if I’m actually
walking around with my device like I am today and
I’m actively using all of the apps on my phone? MEGHAN DESAI: Yeah,
that’s right, Ashish. It turns out that most
of the time our devices aren’t stationary, right? We have them in our
hands, or in our pockets, and we’re moving about the
world doing what we need to do. So we wanted to bring
the power of Doze, the battery gains of Doze,
to that situation as well. And that’s why we’re extending
Doze in the Android N-release. So let’s take a look at
how that’s going to work. Again, think of these orange
bars as background activity. And at some point, you
turn the screen off. And you put the
phone in your pocket. So it’s not being
charged right now. Well, shortly after
that, and this time on the order of minutes,
so shortly after that, the first phase
of Doze kicks in. And now, this is a
lighter, gentler Doze than what you saw with
Marshmallow in that it’s only going to restrict the
application’s network access, and any of these jobs and
syncs will get deferred. When do they get deferred
to, you might ask? To the next maintenance window. So sort of the familiar
maintenance window and Doze repeated cycle
will ensue after that so long as the screen
continues to be off. And again, the idea here is that
we’re balancing battery life with freshness of content. And in the maintenance
windows, these restrictions are lifted to allow any
pending activity to resume. And all this will end
when the screen comes on, or you plug in the device,
as you would expect. OK. So let’s quickly review the
Doze that we just talked about in Marshmallow and figure out
how this extended Doze that I talked about will
work with the Doze that I talked about
in Marshmallow. So for that, we’re going
to zoom into this red box on the screen. Let’s take a look
at what happens. So as you’d expect, the
device is stationary. It’s on battery. And it’s screen off. But the amount of time hasn’t
passed yet for Doze to trigger. Only a few minutes have passed. At this point, this extended
Doze, or this lighter, gentler version of Doze
will kick in, the N-release. And you’ll see that same pattern
of Doze and maintenance window. And at some point, the
device will realize, oh, hey, the device actually has been
stationary for quite some time. And it’s been stationary
for the amount of time required for Doze to kick in. And then, at that point, just
like it does in Marshmallow, the full set of Doze
restrictions will kick in. So at that point, applications,
again, will Wakelocks, their alarms will get
deferred, and there’ll be no more GPS or Wi-Fi
scans because the device has been stationary. Great. So we were very excited
about the battery life gains of this extended Doze. But the even better
news for all of you is if you’ve already
optimized your applications for Doze and App Standby, you
don’t need to do too much more. High-priority Firebase
Cloud Messaging messages continue to provide the
application temporary Wakelock and network access. And foreground services continue
to be exempt from Doze and App Standby. So we make sure that
Ashish’s music keeps playing. ASHISH SHARMA: All right. MEGHAN DESAI: Cool. So we’ve been talking a lot
about background services and their impact
on battery life. We’re going to switch
gears a little bit and talk about background
services and their impact on memory. So let’s say you’re trying
to do something on your phone and it’s just really
slow and sluggish. Say you’re trying to take
a picture with the camera, and you miss that moment because
your phone was just too slow. You know what I’m talking about. Background services have an
impact when the screen is on, as well. And that’s what we’re
going to focus on next. So again, let’s say
you have an application you’re trying to use,
that’s the Top App here. At any given time,
there’s a number of things happening in the
background, lots of stuff happening in the
background services. When a device enters a
low memory situation, or if it just happens to be a
low memory device, what happens is there’s not enough
memory to run all that stuff in the background
while you’re trying to use the device with
that thing at the top. Well, at that point,
Android is too busy trying to swap applications
in and out of memory to let them do what they need
to do in the background, which applies pressure on the
application you’re actually trying to use. And the net result is that
you get this frustrating, slow experience of the device. So that’s the problem
we’re trying to tackle. But background work
is pretty important. So let’s figure out why
background work is happening. One such trigger for
background service is something called
an implicit broadcast. A broadcast is
just a signal that gets sent out on the device
whenever something happens, the minute something changes. And the implicit
type of broadcast is the type that
gets sent to any app, or any application
can listen to it, versus the explicit side, which
would be something that gets sent to a specific application. What makes this particularly bad
is that often these broadcasts are listened to, the
receivers for these broadcasts are declared in a static
way in the application’s manifest file. What that means is that the
application doesn’t actually have to be running for it
to receive this broadcast and react to it. In fact, a broadcast
sent in this manner would cause the applications
that are not even running, but listening
for it, to be woken up, brought into memory, and
react to it in some way. And while Android is
too busy doing that, the application that you’re
actually trying to use starts to be sluggish and slow. Let’s take a quick
example of this, a broadcast called
CONNECTIVITY_CHANGE. This is a broadcast that
gets sent quite frequently on your device. You know, any time you
switch from Wi-Fi to cell, or back, or any kind of
connectivity change happens, this broadcast gets sent. And it turns out, a
lot of applications listen to this broadcast
in a static way, by declaring receivers
in the manifest file. And so, whenever this
broadcast gets sent, lots and lots of
applications are woken up to perform activity
in the background. And you get a frustrating
experience on your device. So this is the problem
that we’re trying to solve. So what do we do? Well, we could just get
rid of background services and implicit broadcast
in Android All right. It’s not that simple. Because background activity
is actually pretty important. So what we’re
envisioning here is that applications perform
any background activity using exclusively JobScheduler jobs. And they reduce their reliance
on background services and statically
declared receivers for implicit broadcasts. Let’s take a quick
look at what I mean. So what we envision here is
that applications’ statically declared implicit broadcast
receivers would no longer get woken up. One time declared receivers
would continue to work. Explicit broadcast
receivers would continue to work, both declared
statically, or at one time. But the statically declared
implicit broadcast receivers would be the ones that
are specifically affected. Second, for background
services, we envision that apps are no longer
running background services, or dependent on that for any
kind of background execution. Now, I said, background
execution is important. And for that, we want developers
to use JobScheduler or Jobs. Now, foreground services
will still continue to work. So, Ashish, your music will
still continue to play. ASHISH SHARMA: Well, thank
you for that, Meghan. But all of this
sounds pretty scary. These are pretty big changes. Are they coming in N? Do we need to change
all of our apps in time for N,
which is very soon? MEGHAN DESAI: It’s
not coming in N. But you need to
change your app soon. So today, we’re just
giving you a preview of what we envision to
be the future of Android, where we think Android is going
with respect to background activity. We know that background
activity plays a huge factor in
both battery life and the overall
performance of the system. So this is sort of
where we are going. And we’re planning
to launch these when we think
they’re going to be ready in some future release. And they’ll apply to the apps
that target that release. In the N-release, we want to
give you tools to start testing your applications under those
conditions and giving us feedback on, as you think about
changing your applications to use job scheduler,
where you can’t. We’re also removing
a few broadcasts that we think are particularly
harmful in the system today. And I’ll talk about
that in just a second. So we have some adb commands
you can use today in the preview and apply them to
your application. Start testing to see what
happens, how your applications behave under these conditions. And send us feedback. Let us know what implicit
broadcasts that you’re currently dependent
on in your manifest files that you
can’t live without, what kind of background
services use cases you have that you can’t move over
to job scheduler or jobs. OK, Ashish, so I think your
specific question was what’s actually going to be
changing in the N-release, so let me talk a
little bit about that. First, I already talked
about CONNECTIVITY_CHANGE as being a particularly
harmful broadcast. So that’s one that
we’re getting rid of. So applications that are
targeting the N-release will no longer be woken up as
a result of this broadcast. This means that if you’ve
declared a receiver for this broadcast in
your manifest file, that’s no longer going to work. If you declare it at
runtime, as I said, runtime receivers
for broadcast will continue to work because
your applications are already running at that point. And for other use cases, we
want you to use JobScheduler. And JobScheduler already has
network trigger semantics. The other two are
NEW_PICTURE and NEW_VIDEO. These are two more
implicit broadcasts that are sent right when
the user takes a picture. And they’re sent by the camera. And that’s sort of
the worst time when you want a lot of
other background stuff to be happening because
you want to focus on taking that next picture, or
whatever it is you’re doing with the camera application. So starting with the
N-release, all applications will no longer be able
to send or receive these two broadcasts. So not just those targeting
N, all applications. And in fact, these
broadcasts are actually pretty important because they
unleash some pretty cool use cases. So one of them is
uploading photos. As soon as you take a photo,
you want that uploaded. But maybe you can wait. And so for that, we’re
actually expanding JobScheduler to be able to be
triggered on content provider changes. So the media folder has
a content provider URI. That could be the trigger
whenever something updates there to upload that photo. And the cool thing
about this is that now, because you’re using
Java scheduler, the system can optimize when
that action takes place. It doesn’t have to
happen immediately when you’re trying to
take that next picture. It can find the next
opportune time to do it, depending on the
memory conditions. Cool. So I’ve been talking a
lot about JobScheduler and how awesome it is. But just a show of
hands, how many of you have actually heard
of JobScheduler? ASHISH SHARMA: Well,
that’s a good number. But I also see a lot of
the hands that are not up. So maybe it’s a good
time for us to review what this really important
JobScheduler API really looks like and what the features are. Because you made it
sound very important. OK. Let’s do a quick review
of the JobScheduler API so that everyone here
is on the same page. The JobScheduler
API, think of it like a wrapper around
any background activity. So any background sync,
any background activity that you have,
JobScheduler is the way to think about scheduling those. And this is slightly a paradigm
shift, where what you’re doing is you’re letting Android know
that I have some tasks that need to get done, and you
specify certain triggers when Android will schedule
those jobs for you, rather than something that you
try and take care of yourself. So let’s take a
couple of examples. These triggers, when you request
Android to schedule your job, could be used on a
certain time window. So say you have a job that’s
important, not exactly urgent. It doesn’t need to
happen right away. You can tell Android
that, schedule this job any time within
the next one hour. And what Android would do is
once many applications are using the JobScheduler
API, it now has this context about
all the background activity from the different
apps that needs to happen. And it’s going to do a good job
at scheduling your job at just the right time, so
that the efficiency of the CPU and the networking
radios can be maximized. Now, what you can also
do is specify triggers based on network connectivity,
or the type of network that becomes available. So say, for example,
an application that’s uploading a whole
bunch of photos or videos that you might
have on your phone, now, it’s a very good
idea for such an app to schedule or to specify a
trigger for of Wi-Fi network. Because what that’s
going to do is, Wi-Fi typically
has more bandwidth. And it’s less expensive,
in terms of money. And it costs also less power
than the cellular radio. So that can be a
constraint, or a trigger, that you can specify. And finally, the thing which is
my favorite, which comes back to the whole deferring until
the device is on charger, you can specify
that control too. So you can tell
that here’s a job that I want to get
done and trigger it when the device is charging. But not just that. Because every time you
plug in the device may not be the best time for all
of the background jobs to start firing up. Say, for example, I saw
some power outlets outside. You’ve been here since morning. Your phones are running low. And you find that power outlet. And you plug in your device to
get maybe 5 minutes of charge. And right then, if all of the
photos and the videos that you took today start getting
uploaded to the cloud, that’s going to be a not so
pleasant experience for you. Because your device
might get slow. But also, you might not get
enough charge out of the outlet because you’re spending
all of that energy. So what you can
do is you can say the device should be
charging and should be relatively unused. Now Android’s smart
enough to figure out when you are not
actively engaged or interacting with your device. So it’ll wait a little
while, make sure that this is a nice
time to schedule all of those background jobs,
and it will trigger your job right then. So we have seen that the
JobScheduler API is really important and it will
help you optimize, defer, and coalesce your
background activity, not just based on battery
constraints or connectivity conditions, but also,
in terms of memory. So let’s take a look at a quick
example of how the JobScheduler API works and how easy it
is, in a few lines of code, to get your jobs done. I’m showing you
a JobInfo object. Let’s create an object
using a builder. We can specify a required
network capability to be that of network
type Unmetered. Now, what that
typically translates to is a network that doesn’t
cost the user money. And most Wi-Fi networks
fall into that category. So in a way, you’re specifying
the Wi-Fi connectivity here. What you are doing then is,
say I want my job, or my app, to sync up with my cloud
backend server every 24 hours. It doesn’t have
to be by the hour, but once every day
is fine for me. So what I’m going to do is set
up a periodicity of 24 hours. And here comes
the favorite part, which is, you do this when
the device is on charger. So you specify the set
requires charging constraint. And those four lines, you can
schedule a job and it’s done. Now, Meghan also talked about
something very interesting and an extension to
the JobScheduler API that we’re introducing
in N, and that is to take into account
the memory conditions, or the RAM conditions
on your device. So now, JobScheduler
also supports triggers based on
content provider updates. So the example that
Meghan gave was, if you’re trying to take
a picture, or that selfie, or of your kid, and
if at that moment, you’ve just taken a picture and
you want to click another shot, and if your phone
gets low, then that may not be a good
time for you to start uploading your pictures. And what you can do is now
you can tell JobScheduler that I’m listening for this
content provider update when a new picture appears. But there’s a little bit
of wiggle room there. It doesn’t have to start
right at the very second when the picture was taken. And the JobScheduler API
is intelligent enough to prioritize all of the
jobs for the processes, or for the application
that is in the foreground, or that is running
foreground service, to account for the fact that if
you’re interacting with an app, all of the jobs for
that particular app should get priority, an
automatic priority, or all of the other jobs that may
not be as time critical. And finally, JobScheduler is
aware of the available RAM on your device. So depending on how
much RAM is available, it might choose to schedule
more than one job at the time. Or, if the memory
conditions are not ideal, or if you are running
low on memory, then only a few jobs, or
the top priority jobs, will get scheduled first
before all of the other ones get precedence. So these changes
are interesting. Let’s take a look at
a quick code sample of how you want to use the
JobScheduler API for something like a NEW_PICTURES
content provider update. You get an instance of
your JobScheduler service. You create a builder object. And you specify now, instead
of in the last example, where we had specified
constraints on the network type and the periodicity,
what we add here is a trigger for a ContentUri
update for NEW_PICTURE. And you can schedule your job. And that’s it. You’re done. So this is all good. JobScheduler API was introduced
in Lollipop, which was API 21. We also have, and have
had for awhile, a backward compatibility library,
which lets you do almost all of those same things that I
talked about on devices that may be running a previous
version of Android, or an earlier
version of Android, and that is Google
GCMNetworkManager. Wait. This slide doesn’t
say GCMNetworkManager. Meghan, what did you do? MEGHAN DESAI: Yeah,
yeah, that’s right. It’s actually Firebase
JobDispatcher. So today, as part of the
Firebase announcements, we’re launching
Firebase JobDispatcher, which was formerly known
as GCMNetworkManager. The cool thing about
Firebase JobDispatcher though is that
it’s an open source SDK that is, effectively,
providing you the same capabilities
that JobScheduler does in the platform, but in
a backwards compatible way. That is, it’s a wrapper,
again, for background activity. It’s available not
only on Android, but coming soon, also, on iOS. And it, on Android pre-Lollipop,
Google Play Services will act as the central
scheduling driver. On Lollipop and onwards, where
JobScheduler is available, it will just use JobScheduler. And then, on iOS, it will
use Grand Central Dispatch. So that’s pretty cool. Let’s take a quick
example of what JobDispatcher looks
like when you’re performing background activity. So this is a quick example
of creating a simple job service that encapsulates
a code you need to perform in the background. This is the, whatever it is that
your application needs to do, in the background, you put
in that doWork function. And then, again, very simple,
create a job using the Job Builder from the Dispatcher. Give it the service
that you just created that’s wrapping
around all the activity. And then, in this case,
I’m just giving it a constraint that I want it to
happen on an Unmetered network. And then, that’s it. Then schedule. So pretty simple,
very easy to use to perform any kind of
background activity. So Ashish, we’ve been talking
a lot about very cool platform features, a lot of APIs
that we’ve introduced. And these sound like they’re
going to have a huge impact. But how can we be
sure that they’re going to make any difference? ASHISH SHARMA:
That’s right, Meghan. It’s not an easy
problem, something that I have personally suffered
with, or struggled with, for a while, and that is,
how do you really make sure that your app is
behaving the way that you intend it to be when
it comes to all of these battery optimizations? Or worse, what if your app
is draining more battery than you think it should? How do you diagnose that? So let me take a quick poll. How many of you have tried
diagnosing battery problems on your applications? MEGHAN DESAI: OK. Quite a few. ASHISH SHARMA: Some. Now, for the others who
did not raise their hands, was that because you
found it too hard to diagnose battery problems? Because I’ve been
in that same place. Well, you can be honest, but, so
diagnosing of battery problems can be really
tricky [INAUDIBLE]. And good thing we have a tool. And we have some logs
on the device that can help us do that
in an easier fashion and not have to struggle
through all of the pain. Let’s look at some of the
logs, or the types of logs, that are present on the device. Now, Android maintains
data structure in memory on all devices. And this log is
called Batterystats. Now, what Batterystats is is it
is a set of cumulative counters that go on incrementing while
your device is on battery. So since it’s in
memory, and these are cumulative counters
that go on increasing, they need to get
reset at some point. And that point is when you’ve
fully charged your device, and you’ve just unplugged it. So say, for example, you
charge your device overnight. And you unplugged it
at 7 AM in the morning. And maybe it’s about 10 and
a half hours since then. If you take a bug report
on your device now, then it would contain the whole
10 and a half hours’ worth of Batterystats and counters
about various things happening on your device that we think
are relevant with respect to battery life. So things like how long
was the partial Wakelock held on the device
across all applications and on an application basis? Or how much data was transferred
over the mobile network or the Wi-Fi network? And what you can see
here is there’s also a StartClock time which tells
you exactly when the stats were reset. So this is really
useful when you’re trying to look at what all
happened on your device that may have caused the
battery to drain faster than what you would expect. The other type of log that
is present on the device is something that we
call Battery History. And what this is,
it is an event log of all of the state transitions
for components on your device, or for actions like
scheduling a wakelock, or an application
scheduling a job, or the device going into
suspend, coming out of suspend, or maybe it’s the network
radio that got turned on. So there’s a lot of
information here. And this would contain an event
log of a millisecond level granularity of everything
that happened on your device since the stats were reset. MEGHAN DESAI: A millisecond
level granularity? You’re telling me that
I have to look at this to figure out what’s going
on with the battery life on my device? ASHISH SHARMA: Yes. MEGHAN DESAI: There’s going
to be hundreds of thousands of lines of this. ASHISH SHARMA: Well,
but it’s fairly obvious. You can just make out
what the problem is. MEGHAN DESAI: Well, can I? ASHISH SHARMA: No,
I’m just kidding. We have a tool
that helps us make sense of this entire thing. And that’s called
Battery Historian. Many of you might
be aware of this. And what this tool would
do is it would take all of those logs
that are present, the two logs that
I just mentioned that are present
in the bug report, and it would help
you look at them in a very intuitive and
interactive UI that makes clear what the problem
is on the device. So Meghan– MEGHAN DESAI: Wow. That’s pretty cool. I like this. I like this a lot. So where do I see this though? Is this on my device
and setting somewhere? ASHISH SHARMA: No. I know you have a very
cool and powerful device, but going through these hundreds
of thousands of transitions on your small little
screen may not be a very pleasant experience,
especially when you’re trying to diagnose battery
problems with your apps. So what this is
is, let me walk you through the workflow
of how this tool works. It is an open source
tool available on GitHub, ready for you to download. And you can look
at the source code, modify it any
which way you want. What you do is, you install
it on your computer. Now, you have your
development device on which you, for the
stats to be recent, because you want to have
a good starting point, you can either charge
the device up to 100% when the stats would get reset,
or there is an ADB command to actually manually
reset the start so you have a good initiation point. You can run your
experiment, which might last a few minutes,
or maybe a couple of hours. And at the end of it,
you take a bug report. And then, you upload that
bug report on your computer that you have the
Battery Historian tool to go back to this interactive,
visual interpretation of all the state transitions. MEGHAN DESAI: Cool. ASHISH SHARMA: So now that we’re
clear on how the workflow works for Battery Historian,
I’d like you to come with me on a
slight tour of what are the features of this tool. Let’s zoom into one of the
rows, or a few of these rows. What you’re seeing is the top
line, which is CPU running. And what this indicates
is it indicates is whether your
device was in suspend, or was it out of suspend? So the solid black bars are
when your device was actually out of suspend and
doing some activity. Similarly, you can
see things like when was a Userspace Wakelock held
or when the screen was on. And the information about
any of your jobs or syncs will also appear here. And in this UI, you can zoom
in to every little event that you see, no
matter how long. And if you take your
cursor over that, it will show you a nice tutor. So say, for example, we are
at this point in the UI. We have zoomed in. And it tells me exactly
what the current time was at this instance. And the red
highlighted portion now shows you the battery
level drop from 73 to 72 and how long it
took for the device to discharge from
73 to 72, giving you an indication of what
the average discharge rate was during that time. And you can see all of the
events lined up nicely. So you can actually
figure out when your device was discharging
rather fast, what were the events that were
happening on the device? Let me take you through
another example. So say you have
adopted or migrated your app to start
using JobScheduler now. How do you figure out when your
jobs are getting scheduled? So in the JobScheduler row, you
go on any one of those events. And if you are in
a zoomed out view, it might collapse a bunch
of these little jobs that didn’t last as long. But it will give you
information about how many jobs were run in that particular
small box and for how long each of those jobs ran. And you can zoom in if you like. So it’s a very
interactive and fun tool. I have a lot of
fun playing with it and diagnosing all
the battery problems. What I want you to do is look
at an example of Doze in action. So we’ve been talking about the
Doze mode in Marshmallow that was introduced and the lighter
version of Doze that was introduced in the N-release. So what I’m showing you
here is a bug report that I uploaded to the
Battery Historian tool. And the black line that
you see going down that’s not exactly horizontal, that’s
your instantaneous battery level. So typically, it would start
off with something high if you started with 100%. In this case, I manually
reset the stats. It starts somewhere around 50%. And then, what you
can see is, let’s zoom into this little area. When your screen
was on, you can see that the frequency of your
jobs and syncs was fairly high. All of the jobs and
syncs were getting scheduled fairly periodically. But then, after the
screen has been turned off for a while, what you see in
the Doze line, or the Doze row, in orange, that’s the lighter
version of Doze kicking in. So some applications
would lose network access. And you start to see that
now your jobs and your syncs are beginning to get
less and less frequent. And they’re getting
batched together. And further out, after the
device has had its screen off for a while, and it
has been stationary, you see the device entering
this deeper Doze mode, which is shown in the blue row here. And when that
happens, now, we know that the device is not
being touched by the user, is not being used. And that’s an opportunity
for the JobScheduler API to start throttling and batching
together a lot of the activity. So you see that
under the blue bars, the JobScheduler and the
SyncManager frequency is fairly infrequent. And they get scheduled during
the maintenance windows. Now, what’s really
interesting is– and this slide will help you
get a perspective on what uses the most power on
your phones– initially, when the screen was
on, my battery level was discharging really fast. So you see the
slope of the line? That’s my battery level going
from 50 to maybe 30 very quickly. And after the screen
has been turned off and the Doze mode
has kicked in, that’s when you start to see
that now my battery is not declining as fast. And it might have even lasted me
a couple of hours in that state without discharging a
whole lot of battery. And then, towards
the end, as soon as the screen is
turned back on, we see that the device
exited the Doze mode. And you go back to
that steep discharge of when I’m actually playing
a game or watching a video. MEGHAN DESAI: That’s
pretty cool, Ashish. So all that stuff we were
talking about, coalescing, and deferring background
activity during Doze actually works. ASHISH SHARMA: That
is living proof. MEGHAN DESAI:
That’s pretty cool. ASHISH SHARMA: OK. So the next thing
I want to show you is, I talked about
these accumulated stats. So the same tool, what
it would help you do is, once you’ve
uploaded the bug report, it will now show you all of this
information that was collected on the device, so
which jobs were run, for how long
they were run, which application required Wakelocks,
and for how long they did. And in general, for
the entire device, there’s a whole bunch
of information here, such as the mobile radio
activity, which application used the most amount
of mobile traffic or Wi-Fi, number of Wi-Fi scans. And it helps you
get a good overview in a very quick
fashion on what exactly happened with your device. MEGHAN DESAI: So hold on. This has all been pretty cool. But I thought you said that this
was going to help me figure out issues with my application. ASHISH SHARMA: Yes. MEGHAN DESAI: Can I
do that with this? ASHISH SHARMA: Yes, Meghan. That leads me to
my very next slide, which is, there is an
App Selection bar there. So you can actually search for
your app and pick your app. And the moment you’ve done that,
you get taken to this App Stats view, which tells you all of
this same information just for your app. So you can look at
all the jobs that got fired, what all
processes you were running, how much mobile
data, or Wi-Fi data, sensors, all the good stuff
just there for your app. And the very cool thing
that I don’t have it here in the slides is once
you’ve picked your application, if you go back and look to the
UI of the timeline of events, you will see that in the job
row, or the JobScheduler row, or the Sync row, only the jobs
and syncs for your applications will appear. And all else will disappear. So that can really get you a
visibility into how frequently your application was
scheduling all of these tasks. So we found this tool
to be very useful. But there is one case that has
been especially painful for me. And that is, when you
are developing an app, or say you made a
change in your app, and suddenly your device
is discharging very fast. Now, I write perfect code. I never make mistakes. But then, my device
is discharging fast. What did I do? And I’m in this position more
than I would like to admit. And I’m sure a lot of us have
been in this situation for one, or the other, time. And so for that, what we
have is an A/B Comparison mode in the same tool. So what you can do is you
can upload two bug reports. And if you have a good case
and you have a bad case, then what the tool
will let you do is it will highlight
all the biggest differences that it sees
between these two bug reports. So say, for example,
it’s comparing now file 1 versus file 2. And it’s telling
me that in file 1, it has used 7.5 times more
Wi-Fi data than the others. And the screen off
discharge rate on, let’s say, the first one,
was less than 2.5 times, and a whole lot of
other good stuff. I haven’t shown you
all of the detail. But if you upload
two bug reports, it will automatically normalize
those two bug reports. So say, if you have
one bug report that was taken for four hours, and
the other that was at two, it will automatically
normalize all of that and show you a good
comparison, which can give you a very good starting point
as to what actually changed on the device, whether
it was really my app, or some other app started
doing something that may have accounted for this difference. So that’s an interesting mode. And to wrap up, I’d
like you to look at one last feature
on this tool, which is my personal favorite. And this is for the
true geeks out there. So if you have a
phone, and if you were able to modify your
phone to connect it to a power monitor, and say
you were recording the instantaneous current values
when the device was actually running. What you can do is you
can upload a bug report, and you can upload
these power readings, these instantaneous
current values, to the Battery Historian tool. And it will show
you a nice overlay of what your instantaneous
current draw was and what the device was
actually doing at the time. So here’s, you know, this
is where for me, at least, all of it comes together. So you see when the CPA
was running, indicated in the black bars in
the top row, that’s when your instantaneous
current draw was close to 800 milliamperes. But when the device
was in suspend, it was hardly anything. You can’t even see it there. Because it’s close to
about 4-5 milliamps. So there’s several orders
of magnitude difference in the amount of power that’s
discharged from your phone when you’re actively
doing stuff. And when you do this, when
you use the JobScheduler API and start batching together
a lot of the activity, well, it’s not hard to see that
your phone will now last much longer and really take away the
pain from having a device that doesn’t last as long. MEGHAN DESAI: That’s
really cool, Ashish. I’d love to have an
amp meter to look at what’s going on my phone. ASHISH SHARMA: Yeah. There are detailed instructions
of this on the GitHub website on how to actually hook it up. So try it out if you like. MEGHAN DESAI: Cool. So what’s next? Well, you saw how these simple
design principles that Ashish talked about, Reduce,
Defer, and Coalesce, go a long way in improving
battery life and performance of the device. So here’s what we
want you to do. We want you to reduce
all the background activity in your applications. What you can’t reduce, defer it
to when the device is charging. And what you can’t defer to
when the device is charging, at least help us coalesce it
with other activity that’s going on in the background. So go out there
and figure out how to use JobScheduler and
JobDispatcher instead of using background services. We actually have a
code lab up to walk you through some key use
cases around migrating from services to JobScheduler. Check out Battery Historian,
as Ashish mentioned. We also want you to start
removing your dependencies in your applications
on statically declared implicit broadcast receivers,
as well as on any background services, again. And send us any
feedback as you’re doing that on where you
are unable to do that using JobScheduler or JobDispatcher. We would love to hear from you. We want to get there together. So with that, if you
have any questions, you can join us at office
hours right after this, at 6 o’clock on stage 9, as
well as tomorrow and Friday. Thank you so much for
being here this late. ASHISH SHARMA: Thank
you for coming. [APPLAUSE] [MUSIC PLAYING]

Author:

20 thoughts on “Android battery and memory optimizations – Google I/O 2016”

  • When they say that "App can no longer run unbound background services", does this mean that IntentService will no longer work??

  • "Remove dependency on unbound background services", does this means that prefer to use "bindService" than "startService"?

  • Thats great, but +Google, the Number 1 battery eater for me is always Google Play Services…

    Are you not using your own APIs?

    Take a look at for example: CmaSystemUpdateService

  • Kushal Pandya says:

    You guys have great APIs (eg; JobScheduler) that enable apps to reduce battery consumption, but a crappy app approval system which doesn't really observe app in a long run that how's power consumption is handled so no matter how many Dozes you throw at Android, standby time will remain shitty unless you tighten the grip on app approval system of Play Store to make sure that app targetting Marshmallow and higher strictly abides by battery saving mechanisms.

  • nitinKmrdixit says:

    can google restrict running of background app and their services which run automatically and forcefully ? these cost lot of RAM and Power.

  • Babubhai Apte says:

    Seems like lot of stuff to consider before and that is because of other apps failed to do their part of moderate battery usage 😛

  • Carlos V. Gonzalez says:

    So Google is copying what apps like Sony Stamina, DeepSleep Battery Saver or Greenify does. Google have been doing an awful job on project Volta until now has been a disaster. Maybe Google should buy the Code from those apps, because of all limitations the OS has they have been doing a heck of better job than project Volta or Doze.

    Also it seems a nightmare for developers, Dozens of APIs out, apps broken on new Android version, closed Push Service, a nightmare in China as the Google Services Battery Hog is not installed by default, wow, Google, put your self together!

  • JONATHAN LUCERO says:

    I' having some trouble with a application with this isIgnoringBatteryOptimizations flag, is always returning false, I don't know what's going on, I don't know what to do, I really hope you can help me

  • TheHeartMachine says:

    Why should app devs care when Google doesn't do what's peached here? Take Google Photos for example, now there's no longer an option to only do sync when charging. Why? WTF?

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