Nick
On Fri, Apr 21, 2017 at 4:25 PM, Ehsan Akhgari
<ehsan.akhg...@gmail.com <mailto:ehsan.akhg...@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
<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
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