Quantum Flow Engineering Newsletter #6

[Ehsan Akhgari]

Hi everyone,

I would like to share some updates about some of the ongoing performance
related work.

We have started looking at the native stack traces that are submitted
through telemetry from the Background Hang Reports that take more than 8
seconds. (We were hoping to have been able to reduce this threshold to
256ms <https://bugzilla.mozilla.org/show_bug.cgi?id=1346415> for a while
now, but the road has been bumpy -- but this should land really soon now!)
Michael Layzell put together a telemetry analysis job that creates a
symbolicated version of this data here:
https://people-mozilla.org/~mlayzell/bhr/. For example, this
<https://people-mozilla.org/%7Emlayzell/bhr/20170405.html> is the latest
generated report. The grouping of this data is unfortunate, since the data
is collected based on the profiler pseudo-stack labels, which is captured
after 128ms, and then native stack (if the hang continues for 8 seconds)
gets captured after that, so the pseudo-stack and the native stack may or
may not correspond, and this grouping also doesn't help going through the
list of native stacks and triage them more effectively. Work is under way
to create a nice dashboard
<https://bugzilla.mozilla.org/show_bug.cgi?id=1344003> out of this data,
but in the mean time this is an area where we could really use all of the
help that we can get. If you have some time, it would be really nice if
you can take a look at this data and see if you can make sense of some of
these call stacks and find some useful bug reports out of them. If you do
end up filing bugs, these are super important bugs to work on, so please
make sure you add "[qf]" to the status whiteboard so that we can track the
bug.

Another item worthy of highlight is Mike Conley's Oh No! Reflow! add-on
<https://mikeconley.github.io/ohnoreflow/>. Don't let the simple web page
behind this link deceive you, this add-on is really awesome! It generates
a beep every time that a long running reflow happens in the browser UI
(which, of course, you get to turn off when you don't need to hunt for
bugs!), and it logs the sync reflows that happened alongside the JS call
stack to the code that triggered them, and it also gives you a single link
that allows you to quickly file a bug with all of the right info in it,
pre-filled! In fact you can see the list of already filed bugs
<https://bugzilla.mozilla.org/buglist.cgi?quicksearch=sw%3A%22%5Bohnoreflow%5D%22&list_id=13547427>
through this add-on!

Another issue that I want to bring up is the [qf:p1] bugs. As you have
noticed, there are a lot of them. :-) It is possible that some of these
bugs aren't important to work on, for example because they only affect edge
case conditions that affects a super small subset of users and that wasn't
obvious when the bug was triaged. In some other cases it may turn out that
fixing the bug requires massive amounts of work that is unreasonable to do
in the amount of time we have, or that the right people for it are doing
more important work and can't be interrupted, and so on. Whatever the
issue is, whether the bug was mis-triaged, or can't be fixed, please make
sure to raise it on the bug! In general the earlier these issues are
uncovered the better it is, because everyone can focus their time on more
important work. I wanted to make sure that this wasn't lost in all of the
rush around our communication for Quantum Flow, my apologies if this hasn't
been clear before.


On to the acknowledgement section, I hope I'm not forgetting to mention
anyone's name here!


- Bas Schouten made it so that we don't clear the compositor background
immediately before drawing into it
<https://bugzilla.mozilla.org/show_bug.cgi?id=1352442>. This made some
painting and scrolling related benchmarks faster
<https://treeherder.mozilla.org/perf.html#/alerts?id=5801>, and
fixed a flickering
issue <https://bugzilla.mozilla.org/show_bug.cgi?id=1330814> in the mean
time!
- Mason Chang made the Youtube settings widget less janky
<https://bugzilla.mozilla.org/show_bug.cgi?id=1351733> on Windows with
D2D when the video is fullscreen.
- David Baron made the flushes caused by the code that watches your
mouse to know which side of the window to put the status bar when you hover
a link less severe <https://bugzilla.mozilla.org/show_bug.cgi?id=1307134>
.
- Neil Deakin removed a synchronous layout flush
<https://bugzilla.mozilla.org/show_bug.cgi?id=1334635> that used to
happen when closing a window which would slow down the window going away.
- Dão Gottwald removed some obsolete tab animation telemetry
<https://bugzilla.mozilla.org/show_bug.cgi?id=1345315> which could slow
down tab animations (yes!). Dão also removed a synchronous layout flush
<https://bugzilla.mozilla.org/show_bug.cgi?id=1356655> which could slow
down detaching a tab into a new window and he also lazified some
code to avoid
some more layout flushes
<https://bugzilla.mozilla.org/show_bug.cgi?id=1356663> which were
related to the status panel.
- Markus Stange made the Gecko Profiler not kill your battery after you
stop profiling <https://bugzilla.mozilla.org/show_bug.cgi?id=830990>,
and also made it so that once you start profiling a thread, you can
actually stop profiling it
<https://bugzilla.mozilla.org/show_bug.cgi?id=1346592>.
- Michael Layzell excluded some common file JS file extensions
<https://bugzilla.mozilla.org/show_bug.cgi?id=1352684> from the
expensive computation that we run on Windows to determine the mimetype of a
file from its extension.
- Kris Maglione made it possible to load add-on SDK modules lazily
<https://bugzilla.mozilla.org/show_bug.cgi?id=1314861>. He also
made loading
ExtensionContent.jsm lazy
<https://bugzilla.mozilla.org/show_bug.cgi?id=1317697>. These two
changes together (but probably mostly the former) showed great
improvements on Talos
<https://bugzilla.mozilla.org/show_bug.cgi?id=1314861#c52>. This is
even true for users without any add-ons using the add-on SDK since these
modules are also used in our internal code.
- Robert Helmer created a Go Faster add-on
<https://bugzilla.mozilla.org/show_bug.cgi?id=1356676> to quickly deploy
the fix of bug 1353216
<https://bugzilla.mozilla.org/show_bug.cgi?id=1353216> to Firefox 52
users even before they upgrade to Firefox 53 which includes the fix!
- Edouard Oger made Firefox Sync UI code cache the DateTimeFormat objects
<https://bugzilla.mozilla.org/show_bug.cgi?id=1350613> where possible.
- Alastor Wu made some Fennec media controls code that could be
expensive not run on Firefox desktop
<https://bugzilla.mozilla.org/show_bug.cgi?id=1348803>.
- Makoto Kato added a cache for document encoder objects used by
TextEditor <https://bugzilla.mozilla.org/show_bug.cgi?id=1352882>, in
order to improve the performance of setting the value of
HTMLInputElement.value.
- Tom Schuster optimized Object.hasOwnProperty()
<https://bugzilla.mozilla.org/show_bug.cgi?id=1344469>. This is a
commonly used JavaScript built-in on real web pages, really nice
optimization to have!
- Florian Quèze removed a synchronous layout flush
<https://bugzilla.mozilla.org/show_bug.cgi?id=1353563> that used to
happen when displaying each item in the awesome bar. He improved the
awesomebar even more by caching the one-off search buttons instead of
regenerating them every time we open the popup
<https://bugzilla.mozilla.org/show_bug.cgi?id=1312999>. Furthermore, he
ensured that we don't pay the cost of initializing UITour.jsm for pages
that do not display a UI tour
<https://bugzilla.mozilla.org/show_bug.cgi?id=1349742>.
- Wei-Cheng Pan added telemetry probes for navigation timings and time
to first byte measures
<https://bugzilla.mozilla.org/show_bug.cgi?id=1344893>.
- Shu-yu Guo improved the timing of script source compression by
delaying it until GC
<https://bugzilla.mozilla.org/show_bug.cgi?id=1348134>. Previously we
used to do this when parsing JavaScript (on a separate thread) which is
wasteful because it would mean that we'd have to decompress the compressed
source during page load sometimes, and also burning needless CPU cycles
during JS parsing isn't wise.
- J. Ryan Stinnett made the Developer Toolbar not create a network
listener for every single tab that you have open
<https://bugzilla.mozilla.org/show_bug.cgi?id=1346854>. Besides perf
wins, this means fewer OOM crashes too!

Thanks for reading! Until next time, happy hacking!

--
Ehsan

[Nicholas Nethercote]

Judging from the incoming flow of bug reports, the number of people using
the Gecko Profiler has increased in the last week or two. I take this as a
good sign that it's being used increasingly heavily for Quantum Flow work,
which is good.

Nick

On Fri, Apr 21, 2017 at 4:25 PM, Ehsan Akhgari <ehsan....@gmail.com>
wrote:

> _______________________________________________
> firefox-dev mailing list
> firef...@mozilla.org
> https://mail.mozilla.org/listinfo/firefox-dev
>
>

[Ehsan Akhgari]

On 04/21/2017 03:12 AM, Nicholas Nethercote wrote:
> Judging from the incoming flow of bug reports, the number of people
> using the Gecko Profiler has increased in the last week or two. I take
> this as a good sign that it's being used increasingly heavily for
> Quantum Flow work, which is good.

Yes, indeed. I should also say that this is definitely due to the hard
work of everyone working on improving it both the backend side and on
the UI side (including you!) It's safe to say that this push on
performance could not have happened without the Gecko Profiler, so
thanks to everyone who keeps making it better.

>
> Nick
>
> On Fri, Apr 21, 2017 at 4:25 PM, Ehsan Akhgari
> <ehsan....@gmail.com <mailto:ehsan....@gmail.com>> wrote:
>
> Hi everyone,
>
> I would like to share some updates about some of the ongoing
> performance related work.
>
> We have started looking at the native stack traces that are
> submitted through telemetry from the Background Hang Reports that
> take more than 8 seconds. (We were hoping to have been able to
> reduce this threshold to 256ms
> <https://bugzilla.mozilla.org/show_bug.cgi?id=1346415> for a while
> now, but the road has been bumpy -- but this should land really
> soon now!) Michael Layzell put together a telemetry analysis job
> that creates a symbolicated version of this data here:
> https://people-mozilla.org/~mlayzell/bhr/

> <https://people-mozilla.org/%7Emlayzell/bhr/>. For example, this

> * Bas Schouten made it so that we don't clear the compositor

> background immediately before drawing into it
> <https://bugzilla.mozilla.org/show_bug.cgi?id=1352442>. This
> made some painting and scrolling related benchmarks faster
> <https://treeherder.mozilla.org/perf.html#/alerts?id=5801>,
> and fixed a flickering issue
> <https://bugzilla.mozilla.org/show_bug.cgi?id=1330814> in the
> mean time!

> * Mason Chang made the Youtube settings widget less janky

> <https://bugzilla.mozilla.org/show_bug.cgi?id=1351733> on
> Windows with D2D when the video is fullscreen.

> * David Baron made the flushes caused by the code that watches

> your mouse to know which side of the window to put the status
> bar when you hover a link less severe
> <https://bugzilla.mozilla.org/show_bug.cgi?id=1307134>.

> * Neil Deakin removed a synchronous layout flush

> <https://bugzilla.mozilla.org/show_bug.cgi?id=1334635> that
> used to happen when closing a window which would slow down the
> window going away.

> * Dão Gottwald removed some obsolete tab animation telemetry

> <https://bugzilla.mozilla.org/show_bug.cgi?id=1345315> which
> could slow down tab animations (yes!). Dão also removed a
> synchronous layout flush
> <https://bugzilla.mozilla.org/show_bug.cgi?id=1356655> which
> could slow down detaching a tab into a new window and he also
> lazified some code to avoid some more layout flushes
> <https://bugzilla.mozilla.org/show_bug.cgi?id=1356663> which
> were related to the status panel.

> * Markus Stange made the Gecko Profiler not kill your battery

> after you stop profiling
> <https://bugzilla.mozilla.org/show_bug.cgi?id=830990>, and
> also made it so that once you start profiling a thread, you
> can actually stop profiling it
> <https://bugzilla.mozilla.org/show_bug.cgi?id=1346592>.

> * Michael Layzell excluded some common file JS file extensions

> <https://bugzilla.mozilla.org/show_bug.cgi?id=1352684> from
> the expensive computation that we run on Windows to determine
> the mimetype of a file from its extension.

> * Kris Maglione made it possible to load add-on SDK modules

> lazily <https://bugzilla.mozilla.org/show_bug.cgi?id=1314861>.
> He also made loading ExtensionContent.jsm lazy
> <https://bugzilla.mozilla.org/show_bug.cgi?id=1317697>. These
> two changes together (but probably mostly the former) showed
> great improvements on Talos
> <https://bugzilla.mozilla.org/show_bug.cgi?id=1314861#c52>.
> This is even true for users without any add-ons using the
> add-on SDK since these modules are also used in our internal code.

> * Robert Helmer created a Go Faster add-on

> <https://bugzilla.mozilla.org/show_bug.cgi?id=1356676> to
> quickly deploy the fix of bug 1353216
> <https://bugzilla.mozilla.org/show_bug.cgi?id=1353216> to
> Firefox 52 users even before they upgrade to Firefox 53 which
> includes the fix!

> * Edouard Oger made Firefox Sync UI code cache the

> DateTimeFormat objects
> <https://bugzilla.mozilla.org/show_bug.cgi?id=1350613> where
> possible.

> * Alastor Wu made some Fennec media controls code that could be

> expensive not run on Firefox desktop
> <https://bugzilla.mozilla.org/show_bug.cgi?id=1348803>.

> * Makoto Kato added a cache for document encoder objects used by

> TextEditor
> <https://bugzilla.mozilla.org/show_bug.cgi?id=1352882>, in
> order to improve the performance of setting the value of
> HTMLInputElement.value.

> * Tom Schuster optimized Object.hasOwnProperty()

> <https://bugzilla.mozilla.org/show_bug.cgi?id=1344469>. This
> is a commonly used JavaScript built-in on real web pages,
> really nice optimization to have!

> * Florian Quèze removed a synchronous layout flush

> <https://bugzilla.mozilla.org/show_bug.cgi?id=1353563> that
> used to happen when displaying each item in the awesome bar.
> He improved the awesomebar even more by caching the one-off
> search buttons instead of regenerating them every time we open
> the popup
> <https://bugzilla.mozilla.org/show_bug.cgi?id=1312999>.
> Furthermore, he ensured that we don't pay the cost of
> initializing UITour.jsm for pages that do not display a UI
> tour <https://bugzilla.mozilla.org/show_bug.cgi?id=1349742>.

> * Wei-Cheng Pan added telemetry probes for navigation timings

> and time to first byte measures
> <https://bugzilla.mozilla.org/show_bug.cgi?id=1344893>.

> * Shu-yu Guo improved the timing of script source compression by

> delaying it until GC
> <https://bugzilla.mozilla.org/show_bug.cgi?id=1348134>.
> Previously we used to do this when parsing JavaScript (on a
> separate thread) which is wasteful because it would mean that
> we'd have to decompress the compressed source during page load
> sometimes, and also burning needless CPU cycles during JS
> parsing isn't wise.

> * J. Ryan Stinnett made the Developer Toolbar not create a

> network listener for every single tab that you have open
> <https://bugzilla.mozilla.org/show_bug.cgi?id=1346854>.
> Besides perf wins, this means fewer OOM crashes too!
>
> Thanks for reading! Until next time, happy hacking!
>
> --
> Ehsan
>
> _______________________________________________
> firefox-dev mailing list

> firef...@mozilla.org <mailto:firef...@mozilla.org>
> https://mail.mozilla.org/listinfo/firefox-dev
> <https://mail.mozilla.org/listinfo/firefox-dev>
>
>

[Chris Peterson]

btw, Nathan Froyd is working to add Gecko Profiler support for Stylo's
Rust code and rayon threads in bug 1322656.

[Chris Peterson]

btw, Nathan Froyd is working to add Gecko Profiler support for Stylo's
Rust code and rayon threads in bug 1322656.


On 2017-04-21 8:50 AM, Ehsan Akhgari wrote: