[webkit-dev] Chromium "GPU" LayoutTests

[Adam Barth]

On Mon, Aug 22, 2011 at 3:35 PM, James Robinson <jamesr at google.com> wrote:
> On Mon, Aug 22, 2011 at 3:24 PM, Adam Barth <abarth at webkit.org> wrote:
>> On Mon, Aug 22, 2011 at 3:18 PM, James Robinson <jamesr at google.com> wrote:
>> > On Mon, Aug 22, 2011 at 3:07 PM, Adam Barth <abarth at webkit.org> wrote:
>> >> On Mon, Aug 22, 2011 at 3:02 PM, James Robinson <jamesr at google.com>
>> >> wrote:
>> >> > On Mon, Aug 22, 2011 at 2:55 PM, Adam Barth <abarth at webkit.org>
>> >> > wrote:
>> >> >> I've been trying to wrap my mind around the "GPU" LayoutTests that
>> >> >> Chromium runs.  In
>> >> >> <http://trac.webkit.org/browser/trunk/LayoutTests/platform>, there
>> >> >> are
>> >> >> the following directories:
>> >> >>
>> >> >> chromium-gpu
>> >> >> chromium-gpu-cg-mac
>> >> >> chromium-gpu-linux
>> >> >> chromium-gpu-win
>> >> >>
>> >> >> These seem to be related to the webkit_gpu_tests step on these bots:
>> >> >>
>> >> >>
>> >> >>
>> >> >> http://build.chromium.org/p/chromium.webkit/builders/Webkit%20Mac10.5%20%28CG%29
>> >> >>
>> >> >>
>> >> >>
>> >> >> http://build.chromium.org/p/chromium.webkit/builders/Webkit%20Mac10.6%20%28CG%29
>> >> >> http://build.chromium.org/p/chromium.webkit/builders/Webkit%20Linux
>> >> >> http://build.chromium.org/p/chromium.webkit/builders/Webkit%20Vista
>> >> >> http://build.chromium.org/p/chromium.webkit/builders/Webkit%20Win7
>> >> >>
>> >> >> This file
>> >> >>
>> >> >>
>> >> >> <http://trac.webkit.org/browser/trunk/Tools/Scripts/webkitpy/layout_tests/port/builders.py>
>> >> >> also lists the following bots:
>> >> >>
>> >> >> Webkit Win - GPU
>> >> >> Webkit Win7 - GPU
>> >> >> Webkit Linux - GPU
>> >> >> Webkit Linux 32 - GPU
>> >> >> Webkit Mac10.5 (CG) - GPU
>> >> >> Webkit Mac10.6 (CG) - GPU
>> >> >>
>> >> >> Questions:
>> >> >>
>> >> >> 1) Do these "- GPU" bots exist anywhere?  (I can't find them, and a
>> >> >> recent bug comment indicates that they might be fictional.)
>> >> >
>> >> > The " - GPU" bots are the same bots as the normal layout test bots,
>> >> > but
>> >> > run
>> >> > as a separate step.
>> >> >
>> >> >
>> >> >  See http://build.chromium.org/p/chromium.webkit/builders/Webkit%20Mac10.6%20%28CG%29/builds/185,
>> >> > for example.  The "bot name" for the GPU tests is the normal bot name
>> >> > with "
>> >> > - GPU" appended.
>> >> >
>> >> >>
>> >> >> 2) Are there any other bots related to the GPU configuration other
>> >> >> than those listed above?  (For example, is there any coverage of
>> >> >> this
>> >> >> configuration on build.webkit.org?)
>> >> >
>> >> > build.webkit.org seems to not be running these tests, for reasons
>> >> > that
>> >> > are
>> >> > unclear to me, but they run on the other chromium bots that run
>> >> > layout
>> >> > tests.
>> >> >
>> >> >> 3) Why is webkit_gpu_tests a separate step from webkit_tests?
>> >> >
>> >> > Different flags are passed to DumpRenderTree, but it runs some of the
>> >> > same
>> >> > tests.  This is so we can get coverage for (for instance) the 2d
>> >> > canvas
>> >> > API
>> >> > in our hardware and software paths.
>> >>
>> >> Could we instead use the layoutTestController to enable or disable
>> >> whatever flags at test-time rather than on the command line?  For
>> >> example, we could put the guts of the 2d canvas tests into a
>> >> JavaScript file and include it in two HTML files, one that sets the
>> >> flag and one that does not.  That's how we handle strict vs quirks
>> >> mode, for example.
>> >
>> > There are 802 tests in canvas/philip/tests/ (which is an imported
>> > suite),
>> > currently all implemented as separate .html files, and another 166 in
>> > fast/canvas.  It seems a bit tedious to manually wrap each of these
>> > tests in
>> > two different wrappers.  That doesn't seem like a very practical option,
>> > although it has some nice aspects.
>>
>> I'd be happy to edit these thousand files if it meant we could remove
>> the complexity of the GPU configuration.
>
> You would have to modify all currently existing tests, and all such tests
> that will be added in the future.  I'm not sure how to patch tests that will
> only exist in the future.

Presumably new tests will just follow the pattern of the existing
tests.  Given that we only have 166 of these tests so far, that's not
likely to be too much work.

>>  The ongoing maintenance cost
>> of the GPU configuration strikes me as a lot greater than the one-time
>> cost of changing these tests.  (There's also the side-benefit of
>> letting all the other ports increase their test coverage by wiring up
>> the LayoutTestController method.)
>>
>> I suspect (although I'd have to look more carefully), that we could
>> make this work for the canvas/philip/tests tests without actually
>> modifying the files (e.g., using iframes), if we wanted the ability to
>> easily import new versions of that test suite.
>
> That would seem to imply either running all of the relevant twice for all
> ports, unless this iframe solution was chromium-specific.  Would that really
> be simpler?

Other ports could skip some of these tests, if they desire.  We could
put them in separate directories to facilitate skipping half of them,
for example.

> What concrete costs are you attempting to minimize?  It is difficult to
> modify our tools due to this configuration, but the complexity is restricted
> nearly fully to chromium-specific scripts.  The tests themselves and other
> ports are unaffected.

The complexity is not restricted to chromium-specific scripts.  The
Chromium GPU configuration causes a moderately large amount of
complexity in the common infrastructure shared by the entire project
because it's a special case in many places.  That's why it keeps
breaking when we make changes to the tooling for the project as a
whole.

If we made the changes above, then we'd get the same test coverage
without this added complexity, which looks like a win.

Adam


>> >> >> As far as I can tell, other ports, such as Apple-Mac, make use of
>> >> >> the
>> >> >> GPU but don't impose as large a complexity tax on the project.  Is
>> >> >> there something different about Chromium's GPU support that requires
>> >> >> this additional complexity?
>> >> >
>> >> > Other ports have less test coverage, and they don't run the pixel
>> >> > tests
>> >> > at
>> >> > all on the bots.
>> >>
>> >> Adam
>> >
>> >
>
>