On 6/22/17 6:19 AM, Henri Sivonen wrote:
https://hsivonen.com/test/moz/encoding_bench_web/english-only.html
OK, so here's what I'm seeing on that benchmark, all numbers measured on
Mac with a current nightly; other platforms may differ, etc. Profile at
https://perf-html.io/public/f6a0a4a61edcd784b461d17ea3879c30e03ee7fb/calltree/?implementation=cpp&thread=2
for someone who wants to look themselves, but the numbers below are from
an Instruments profile, because there I can do a much saner job of
coalescing the various codepaths that lead to the functions of
interest... [1]
Out of a total time of 7.6s or so on the main thread, 5.4s is under
TextDecoderBinding::decode. 2.1s is under gcIfRequested. The remaining
time, what there is of it, is almost all under various JS execution bits.
The time under gcIfRequested is almost all under sweeping/finalization.
In fact, it's almost all under arena deallocation. I see 1.7s under
huge_dalloc/chunk_dealloc (on Mac), with most of that (1.4s) being the
madvise calls we make there and another 0.3s calling munmap. Depending
on what it is we're freeing (the GC arenas themselves or the string
data), either nursery allocation for external strings[2] or background
finalization of external strings[3] would help here. The stacks look
like we're freeing gc arenas, but it seems like there would be more
freeing of the string data...
The time under TextDecoderBinding::decode is almost all (5.34s out of
5.4s) under encoding_rs::Decoder::decode_to_utf16 and in particular in
encoding_rs::variant::VariantDecoder::decode_to_utf16_raw. That's all
self time in there. I do see numbers that are much slower than Safari
here, for what it's worth (about 2x), and the 25% of our time spent
under gc is not nearly enough to account for the difference.
-Boris
[1] Not least because of
https://github.com/devtools-html/perf.html/issues/388
[2] https://bugzilla.mozilla.org/show_bug.cgi?id=1375565
[3] https://bugzilla.mozilla.org/show_bug.cgi?id=627220
_______________________________________________
dev-platform mailing list
dev-platform@lists.mozilla.org
https://lists.mozilla.org/listinfo/dev-platform
