Quantum Flow Engineering Newsletter #20

Ehsan Akhgari ehsan.akhgari at gmail.com
Fri Aug 18 05:26:19 UTC 2017

Hi everyone,

It is hard to believe that we've gotten to the twentieth of these
newsletters.  That also means that we're very quickly approaching the
finish line for this sprint.  We only have a bit more than five more weeks
to go before Firefox 57 merges to beta.  It may be a good time to start to
think more carefully about what we pay attention to in the remaining time,
both in terms of the risk of patches landing, and the opportunity cost of
what we decide to put off until 58 and the releases after.

We still have a large number of triaged bugs
%40nobody%40mozilla.org> that are available for someone to pick up and work
on.  If you have some spare cycles, we really would appreciate if you
consider picking one or two bugs from this list and working on them.  They
span many different areas of the codebase so finding something in your area
of interest and expertise should hopefully be simple.  Quantum Flow isn't
the kind of project that requires fixing every single one of these bugs to
be finished successfully, but at the same time big performance improvements
often consist of many small parts, so the cumulative impact of a few
additional fixes can make a big impact.

It is worth mentioning that lately while lurking on various tech news and
blog sites where Nightly users comment, I have seen quite a few positive
comments about Nightly performance from users.  It's easy to get lost in
the details of the work involved in getting rid of synchronous IPCs,
synchronous layout/style flushes, unnecessary memory allocations, hashtable
lookups, improving data locality, JavaScript JIT performance, making sure
code gets inlined better, ship a new CSS engine, etc. etc. but it is
reassuring to see people <https://news.ycombinator.com/item?id=14977352>
take <https://twitter.com/fabi1cazenave/status/898260768419917824> notice

Moving on to mention one point about Speedometer charts on AWFY
which I have gotten a few questions about recently.  We now have
Speedometer benchmark numbers on Firefox Beta on the reference hardware
reported in addition to inbound optimized and PGO builds.  You may notice
that the benchmark score numbers we are getting on Beta are around the same
as Nightly (which swings around 83-84 these days).  This doesn't mean that
we haven't made any improvements on Nightly since the last Beta merge!  We
have some Nightly only telemetry code and some features that are only
enabled on the Nightly channel, and those add a bit of overhead, which
causes us to see a bit of an improvement after an uplift from
mozilla-central to mozilla-beta without any code changes.  This means that
when the current code on Nightly gets merged to Beta 57, we should expect a
bit of an improvement similarly.

And now let me take a moment to acknowledge the work of some of those who
helped make Firefox faster last week.  I hope I'm not dropping anyone's
name mistakenly.

   - Perry Jiang made _shouldCapture() run off of the idle queue and do
   nothing for about: pages
   <https://bugzilla.mozilla.org/show_bug.cgi?id=1353584>. Perry also made
   it so that we don’t unnecessarily load the autoscroll PNG when opening a
   new window.
   - Kris Maglione fixed a recent regression causing extremely poor
   performance with extensions which have scripts creating large numbers of
   message listeners which never call their response callbacks
   <https://bugzilla.mozilla.org/show_bug.cgi?id=1389381>.  He also made
   code that registers a lot of lazy module and service getters use loops
   <https://bugzilla.mozilla.org/show_bug.cgi?id=1388215> to make such code
   easier to optimize by SpiderMonkey JIT.  He furthermore switched away
   from using FileUtils.getFile()
   <https://bugzilla.mozilla.org/show_bug.cgi?id=1388208> which does
   main-thread I/O to check for the respective directory exists.  Kris also
   made us not create the IndexedDB bindings in sandboxes
   <https://bugzilla.mozilla.org/show_bug.cgi?id=1389868> since they’re
   never used and avoided adding the caller location to the sandbox name if
   an explicit name if provided by the caller
   - Jan de Mooij added a megamorphic SetElement stub
   <https://bugzilla.mozilla.org/show_bug.cgi?id=1388388>.  He also optimized
   ToPropertyKey a bit
   - Nicolas B. Pierron optimized the LIRGenerator/CodeGenerator snapshot
   code <https://bugzilla.mozilla.org/show_bug.cgi?id=1388014>.
   - André Bargull removed some unnecessary allocations and rooting in the
   RegExp code <https://bugzilla.mozilla.org/show_bug.cgi?id=1387968>.  He
   also moved Array.prototype.sort entry point to self-hosted JS code
   <https://bugzilla.mozilla.org/show_bug.cgi?id=1383648> in order to avoid
   frequent C++ to JS calls when sorting an array with a comparator argument
   - Zibi Braniecki got rid of expensive per-option element styling that we
   used to have for select boxes in e10s mode
   - Adam Gashlin made us use a low priority timer for Places expiration
   - Henri Sivonen made the HTML parser atomize class attribute values for
   the class of single class values when parsing innerHTML strings
   <https://bugzilla.mozilla.org/show_bug.cgi?id=1375701>.  This speeds up
   parsing HTML strings used in innerHTML setters that have class=”foo”
   - Ting-Yu Chou ensured that we calculate the spill weight of a range's
   uses when we add to or remove from it
   <https://bugzilla.mozilla.org/show_bug.cgi?id=1385165>, as opposed to
   the cache unfriendly iteration over the range's uses to calculate this
   information when needed.
   - Mason Chang got rid of some graphics overhead
   <https://bugzilla.mozilla.org/show_bug.cgi?id=1372602> that we had
   accidentally accumulated on the hidden window on macOS.
   - Edouard Oger ensured that the sync-illustration SVG is not loaded
   until it’s needed <https://bugzilla.mozilla.org/show_bug.cgi?id=1380377>.
   - Jonathan Watt avoided some hashtable lookups in undisplayed maps for
   elements without display:none or display:contents children
   - Blake Kaplan avoided some unneeded sync IPC for performing URI fix-up
   by creating a URI object explicitly in the content process
   - Jonathan Kew avoided some memory allocation churn in

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.mozilla.org/pipermail/firefox-dev/attachments/20170818/37d21619/attachment-0001.html>

More information about the firefox-dev mailing list