On 2013-01-31 6:39 AM, jmath...@mozilla.com wrote:
We then tried to get a sense of how much of a win the PGO optimizations
are. Thanks to a series of measurements by dmandelin, we know that
disabling PGO/LTCG will result in a regression of about 10-20% on
benchmarks which examine DOM and layout performance such as Dromaeo and
guimark2 (and 40% in one case), but no significant regressions in the
startup time, and gmail interactions. Thanks to a series of telemetry
measurements performed by Vladan on a Nightly build we did last week
which had PGO/LTCG disabled, there are no telemetry probes which show a
significant regression on builds without PGO/LTCG. Vladan is going to
try to get this data out of a Tp5 run tomorrow as well, but we don't
have any evidence to believe that the results of that experiments will
be any different.
Are the test run stats we're using here published somewhere? We should be
tracking all this testing some place (a wiki page maybe?) so people can do
their own investigation.
See the dependencies of bug 833881 for the details of the measurements.
I've always wondered if the tests we run during the pgo phase are sufficient to
get good coverage over the entire app. Is it possible that we don't see gains
in other areas because our pgo tests don't hit those areas? (I think there was
an effort under way to expose these tests so they could be modified in try runs
for better experimentation.)
Yes, it's definitely possible to get more PGO coverage, but as far as I
can see, the last time we changed the pageset we load during PGO was in
2009 (bug 472706).
Cheers,
Ehsan
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