[webkit-dev] Introducing run-perf-tests and Adding Performance Bots

Ryosuke Niwa rniwa at webkit.org
Tue Jan 31 15:16:48 PST 2012

FYI, I've added a wiki page describing how to write a new perf. test:

On Fri, Jan 20, 2012 at 11:20 AM, Ojan Vafai <ojan at chromium.org> wrote:
> On Thu, Jan 19, 2012 at 3:20 PM, Ryosuke Niwa <rniwa at webkit.org> wrote:
>> I didn't merge it into run-webkit-tests because performance tests don't
>> pass/fail but instead give us some values that fluctuate over time. While
>> Chromium takes an approach to hard-code the rage of acceptable values, such
>> an approach has a high maintenance cost and prone to problems such as
>> having to increase the range periodically as the score slowly degrades over
>> time. Also, as you can see on Chromium perf bots<http://build.chromium.org/p/chromium.perf/console>,
>> the test results tend to fluctuate a lot so hard-coding a tight range of
>> acceptable value is tricky.
> While this isn't perfect, I still think it's worth doing.

I'm afraid that the maintenance cost here will be too high. Values will
necessarily depend on each bot so we'll need <number of tests>×<number of
bots> expectations, and I don't think people are enthusiastic about
maintaining values like that over time (even I don't want to do that

Turning the bot red when a performance test fails badly is helpful for
> finding and reverting regressions quickly, which in turn helps identify
> smaller regressions more easily (large regressions mask smaller ones).

I agree. Maybe we can obtain the historical average and standard deviation
and turn bots red if the value doesn't fall within <some value between 1
and 2> standard deviations.

In either case, we have to get the bots running the tests and work on
> getting reliable data first.

After http://trac.webkit.org/changeset/106211, values for most tests have
gotten very stable. They tend to vary within 5% range.

- Ryosuke
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