* [RFC/Draft] Testing requirements for upstream drm/i915 patches
@ 2013-10-30 16:00 Daniel Vetter
2013-10-30 18:11 ` Ian Romanick
0 siblings, 1 reply; 5+ messages in thread
From: Daniel Vetter @ 2013-10-30 16:00 UTC (permalink / raw)
To: gfx-internal-devel
Cc: Hindman, Gavin, intel-gfx, Barnes, Jesse, Nikkanen, Kimmo,
Parenteau, Paul A
[This is cross-posted to the public intel-gfx mailing list at
http://lists.freedesktop.org/archives/intel-gfx/2013-October/035268.html
I'll also present a quick overview of this at Gavin's kernel PDT next week.]
Hi all,
So in the past half year we've had tons of sometimes rather heated
discussions
about getting patches merged. Often these discussions have been in the
context
of specific patch series, which meant that people are already invested.
Which
contributed to the boiling emotions. I'd like to avoid that here by
making this
a free-standing discussion.
There's a bunch of smaller process tuning going on, but the big thing
I'd like
to instate henceforth is that automated test coverage is a primary
consideration
for anything going upstream. In this write up I'll detail my reasons,
considerations and expectations. My plan is to solicit feedback over the
next
few days and then publish an edited and polished version to my blog.
After that I'll put down my foot on this process so that we can go back to
coding and stop blowing through so much time and energy on waging flamewars.
Feedback and critique highly welcome.
Cheers, Daniel
Testing Requirements for Upstreaming (Draft)
============================================
I want to make automated test coverage an integral part of our feature
and bufix
development process. For features this means that starting with the
design phase
testability needs to be considered an integral part of any feature. This
needs
to go up through the entire development process until when the
implementation is
submitted together with the proposed tests. For bugfixes that means the
fix is
only complete once the automated testcase for it is also done, if we
need a new
one.
This specifically excludes testing with humans somewhere in the loop. We are
extremely limited in our validation resources, every time we put
something new
onto the "manual testing" plate something else _will_ fall off.
Why?
----
- More predictability. Right now test coverage often only comes up as a
topic
when I drop my maintainer review onto a patch series. Which is too
late, since
it'll delay the otherwise working patches and so massively frustrates
people.
I hope by making test requirements clear and up-front we can make the
upstreaming process more predictable. Also, if we have good tests
from the get-go
there should be much less need for me to drop patches from my trees
after having them merged.
- Less bikeshedding. In my opinion test cases are an excellent means to
settle
bikesheds - we've had in the past seen cases of endless back&forths
where writing a simple testcase would have shown that _all_ proposed
color flavours are actually broken.
The even more important thing is that fully automated tests allow us to
legitimately postpone cleanups. If the only testing we have is manual
testing
then we have only one shot at a feature tested, namely when the developer
tests it. So it better be perfect. But with automated tests we can
postpone
cleanups with too high risks of regressions until a really clear need is
established. And since that need often never materializes we'll save
work.
- Better review. For me it's often helps a lot to review tests than the
actual
code in-depth. This is especially true for reviewing userspace interface
additions.
- Actionable regression reports. Only if we have a fully automated
testcase do
we have a good chance that QA reports a regression within just a few
days.
Everything else can easily take weeks (for platforms and features
which are
explicitly tested) to months (for stuff only users from the community
notice).
And especially now that much more shipping products depend upon a working
i915.ko driver we just can't do this any more.
- Better tests. A lot of our code is really hard to test in an automated
fashion, and pushing the frontier of what is testable often requires
a lot of
work. I hope that by making tests an integral part of any feature
work and so
forcing more people to work on them and think about testing we'll
advance the state of the art at a brisker pace.
Risks and Buts
--------------
- Bikeshedding on tests. This plan is obviously not too useful if we just
replace massive bikeshedding on patches with massive bikeshedding on
testcases. But right now we do almost no review on i-g-t patches so
the risk
is small. Long-term the review requirements for testcases will certainly
increase, but as with everything else we simply need to strive for a good
balance to strike for just the right amount of review.
Also if we really start discussing tests _before_ having written
massive patch
series we'll do the bikeshedding while there's no real rebase pain.
So even if
the bikeshedding just shifts we'll benefit I think, especially for
really big features.
- Technical debt in test coverage. We have a lot of old code which still
completely lacks testcases. Which means that even small feature work
might be
on the hook for a big pile of debt restructuring. I think this is
inevitable
occasionally. But I think that doing an assement of the current state of
test coverage of the existing code _before_ starting a feature instead
of when the patches are ready for merging should help a lot, before
everyone is invested into patches already and mounting rebase pain looms
large.
Again we need to strive for a good balance between "too many tests to
write
up-front for old code" and "needs for tests that only the final review
uncovers creating process bubbles".
- Upstreaming of product stuff. Product guys are notoriuosly busy and
writing
tests is actual work. Otoh the upstream codebase feeds back into
_all_ product
trees (and the upstream kernel), so requirements are simply a bit
higher. And
I also don't think that we can push the testing of some features fully to
product teams, since they'll be pissed really quickly if every update
they get
from us breaks their stuff. So if these additional test requirements
(compared
to the past) means that some product patches won't get merged, then I
think
that's the right choice.
- But ... all the other kernel drivers don't do this. We're also one of the
biggest driver's in the kernel, with a code churn rate roughly 5x
worse than
anything else and a pretty big (and growing) team. Also, we're often the
critical path in enabling new platforms in the fast-paced mobile space.
Different standards apply.
Expectations
------------
Since the point here is to make the actual test requirements known
up-front we
need to settle on clear expectations. Since this is the part that actually
matters in practice I'll really welcome close scrutiny and comments here.
- Tests must fully cover userspace interfaces. By this I mean exercising
all the
possible options, especially the usual tricky corner cases (e.g.
off-by-one
array sizes, overflows). It also needs to include tests for all the
userspace input validation (i.e. correctly rejecting invalid input,
including checks for the error codes). For userspace interface additions
technical debt really must be addressed. This means that when adding a
new flag and we currently don't have any tests for those flags, then
I'll ask for a testcase which fully exercises all the flag values we
currently support on top of the new interface addition.
- Tests need to provide a reasonable baseline coverage of the internal
driver
state. The idea here isn't to aim for full coverage, that's an
impossible and
pointless endeavor. The goal is to have a good starting point of
tests so that
when a tricky corner case pops up in review or validation that it's not a
terribly big effort to add a specific testcase for it.
- Issues discovered in review and final validation need automated test
coverage.
The reasoning is that anything which slipped the developer's attention is
tricky enough to warrant an explicit testcase, since in a later
refactoring
there's a good chance that it'll be missed again. This has a bit a risk
to delay patches, but if the basic test coverage is good enough as per
the previous point it really shouln't be an issue.
- Finally we need to push the testable frontier with new ideas like pipe
CRCs,
modeset state cross checking or arbitrary monitor configuration injection
(with fixed EDIDs and connector state forcing). The point here is to
forster
new crazy ideas, and the expectation is very much _not_ that
developers then
need to write testcases for all the old bugfixes that suddenly became
testable. That workload needs to be spread out over a bunch of features
touching the relevant area. This only really applies to features and
code paths which are currently in the "not testable" bucket anyway.
This should specify the "what" decently enough, but we also need to look
at how
tests should work.
Specific testcases in i-g-t are obviously the preferred form, but for some
features that's just not possible. In such cases in-kernel self-checks like
the modeset state checker of fifo underrun reporting are really good
approaches. Two ceaveats apply:
- The test infrastructure really should be orthogonal to the code being
tested.
In-line asserts that check for preconditions are really nice and
useful, but
since they're closely tied to the code itself have a good chance to
be broken
in the same ways.
- The debug feature needs to be enabled by default, and it needs to be loud.
Otherwise no one will notice that something is amiss. So currently
the fifo
underrun reporting doesn't really count since it only causes debug level
output when something goes wrong. Of course it's still a really good
tool for
developers, just not yet for catching regressions.
Finally the short lists of excuses that don't count as proper test
coverage for
a feature.
- Manual testing. We are ridiculously limited on our QA manpower. Every
time we
drop something onto the "manual testing" plate something else _will_
drop off.
Which means in the end that we don't really have any test coverage. So
if patches don't come with automated tests, in-kernel cross-checking or
some other form of validation attached they need to have really good
reasons for doing so.
- Testing by product teams. The entire point of Intel OTC's "upstream first"
strategy is to have a common codebase for everyone. If we break
product trees
every time we feed an update into them because we can't properly
regression
test a given feature then the value of upstreaming features is greatly
diminished in my opinion and could potentially doom collaborations with
product teams. We just can't have that.
This means that when products teams submit patches upstream they also
need
to submit the relevant testcases to i-g-t.
Intel Semiconductor AG
Registered No. 020.30.913.786-7
Registered Office: World Trade Center, Leutschenbachstrasse 95, 8050 Zurich, Switzerland
This e-mail and any attachments may contain confidential material for the sole use of the intended recipient(s). Any review or distribution by others is strictly prohibited. If you are not the intended recipient, please contact the sender and delete all copies.
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [RFC/Draft] Testing requirements for upstream drm/i915 patches
2013-10-30 16:00 [RFC/Draft] Testing requirements for upstream drm/i915 patches Daniel Vetter
@ 2013-10-30 18:11 ` Ian Romanick
2013-10-30 19:05 ` Daniel Vetter
0 siblings, 1 reply; 5+ messages in thread
From: Ian Romanick @ 2013-10-30 18:11 UTC (permalink / raw)
To: Daniel Vetter
Cc: Nikkanen, Kimmo, intel-gfx, gfx-internal-devel, Hindman, Gavin,
Barnes, Jesse, Parenteau, Paul A
On 10/30/2013 09:00 AM, Daniel Vetter wrote:
> [This is cross-posted to the public intel-gfx mailing list at
> http://lists.freedesktop.org/archives/intel-gfx/2013-October/035268.html
> I'll also present a quick overview of this at Gavin's kernel PDT next
> week.]
>
> Hi all,
>
> So in the past half year we've had tons of sometimes rather heated
> discussions
> about getting patches merged. Often these discussions have been in the
> context
> of specific patch series, which meant that people are already invested.
> Which
> contributed to the boiling emotions. I'd like to avoid that here by
> making this
> a free-standing discussion.
>
> There's a bunch of smaller process tuning going on, but the big thing
> I'd like
> to instate henceforth is that automated test coverage is a primary
> consideration
> for anything going upstream. In this write up I'll detail my reasons,
> considerations and expectations. My plan is to solicit feedback over the
> next
> few days and then publish an edited and polished version to my blog.
>
> After that I'll put down my foot on this process so that we can go back to
> coding and stop blowing through so much time and energy on waging
> flamewars.
>
> Feedback and critique highly welcome.
>
> Cheers, Daniel
>
> Testing Requirements for Upstreaming (Draft)
> ============================================
>
> I want to make automated test coverage an integral part of our feature
> and bufix
^^^^^ bugfix
> development process. For features this means that starting with the
> design phase
> testability needs to be considered an integral part of any feature. This
> needs
> to go up through the entire development process until when the
> implementation is
> submitted together with the proposed tests. For bugfixes that means the
> fix is
> only complete once the automated testcase for it is also done, if we
> need a new
> one.
>
> This specifically excludes testing with humans somewhere in the loop. We
> are
> extremely limited in our validation resources, every time we put
> something new
> onto the "manual testing" plate something else _will_ fall off.
>
> Why?
> ----
>
> - More predictability. Right now test coverage often only comes up as a
> topic
> when I drop my maintainer review onto a patch series. Which is too
> late, since
> it'll delay the otherwise working patches and so massively frustrates
> people.
> I hope by making test requirements clear and up-front we can make the
> upstreaming process more predictable. Also, if we have good tests from
> the get-go
> there should be much less need for me to drop patches from my trees
> after having them merged.
>
> - Less bikeshedding. In my opinion test cases are an excellent means to
> settle
> bikesheds - we've had in the past seen cases of endless back&forths
> where writing a simple testcase would have shown that _all_ proposed
> color flavours are actually broken.
>
> The even more important thing is that fully automated tests allow us to
> legitimately postpone cleanups. If the only testing we have is manual
> testing
> then we have only one shot at a feature tested, namely when the developer
> tests it. So it better be perfect. But with automated tests we can
> postpone
> cleanups with too high risks of regressions until a really clear need is
> established. And since that need often never materializes we'll save
> work.
>
> - Better review. For me it's often helps a lot to review tests than the
> actual
> code in-depth. This is especially true for reviewing userspace interface
> additions.
>
> - Actionable regression reports. Only if we have a fully automated
> testcase do
> we have a good chance that QA reports a regression within just a few
> days.
> Everything else can easily take weeks (for platforms and features
> which are
> explicitly tested) to months (for stuff only users from the community
> notice).
> And especially now that much more shipping products depend upon a working
> i915.ko driver we just can't do this any more.
>
> - Better tests. A lot of our code is really hard to test in an automated
> fashion, and pushing the frontier of what is testable often requires a
> lot of
> work. I hope that by making tests an integral part of any feature work
> and so
> forcing more people to work on them and think about testing we'll
> advance the state of the art at a brisker pace.
>
> Risks and Buts
> --------------
>
> - Bikeshedding on tests. This plan is obviously not too useful if we just
> replace massive bikeshedding on patches with massive bikeshedding on
> testcases. But right now we do almost no review on i-g-t patches so
> the risk
> is small. Long-term the review requirements for testcases will certainly
> increase, but as with everything else we simply need to strive for a good
> balance to strike for just the right amount of review.
>
> Also if we really start discussing tests _before_ having written
> massive patch
> series we'll do the bikeshedding while there's no real rebase pain. So
> even if
> the bikeshedding just shifts we'll benefit I think, especially for
> really big features.
>
> - Technical debt in test coverage. We have a lot of old code which still
> completely lacks testcases. Which means that even small feature work
> might be
> on the hook for a big pile of debt restructuring. I think this is
> inevitable
> occasionally. But I think that doing an assement of the current state of
^^^^^^^^ assessment
> test coverage of the existing code _before_ starting a feature instead
> of when the patches are ready for merging should help a lot, before
> everyone is invested into patches already and mounting rebase pain looms
> large.
This is actually an opportunity in disguise. Once you have identified
some of the places that are really lacking coverage, you give new people
the task to create tests for some small areas. This gives the new
person a way to learn the code and make a contribution without hurting
themselves.
> Again we need to strive for a good balance between "too many tests to
> write
> up-front for old code" and "needs for tests that only the final review
> uncovers creating process bubbles".
>
> - Upstreaming of product stuff. Product guys are notoriuosly busy and
> writing
> tests is actual work. Otoh the upstream codebase feeds back into _all_
> product
> trees (and the upstream kernel), so requirements are simply a bit
> higher. And
> I also don't think that we can push the testing of some features fully to
> product teams, since they'll be pissed really quickly if every update
> they get
> from us breaks their stuff. So if these additional test requirements
> (compared
> to the past) means that some product patches won't get merged, then I
> think
> that's the right choice.
>
> - But ... all the other kernel drivers don't do this. We're also one of the
> biggest driver's in the kernel, with a code churn rate roughly 5x
> worse than
> anything else and a pretty big (and growing) team. Also, we're often the
> critical path in enabling new platforms in the fast-paced mobile space.
> Different standards apply.
>
> Expectations
> ------------
>
> Since the point here is to make the actual test requirements known
> up-front we
> need to settle on clear expectations. Since this is the part that actually
> matters in practice I'll really welcome close scrutiny and comments here.
>
> - Tests must fully cover userspace interfaces. By this I mean exercising
> all the
> possible options, especially the usual tricky corner cases (e.g.
> off-by-one
> array sizes, overflows). It also needs to include tests for all the
> userspace input validation (i.e. correctly rejecting invalid input,
> including checks for the error codes). For userspace interface additions
> technical debt really must be addressed. This means that when adding a
> new flag and we currently don't have any tests for those flags, then
> I'll ask for a testcase which fully exercises all the flag values we
> currently support on top of the new interface addition.
>
> - Tests need to provide a reasonable baseline coverage of the internal
> driver
> state. The idea here isn't to aim for full coverage, that's an
> impossible and
> pointless endeavor. The goal is to have a good starting point of tests
> so that
> when a tricky corner case pops up in review or validation that it's not a
> terribly big effort to add a specific testcase for it.
In Mesa we've started adding tests in Mesa (run with 'make check') in
addition to the piglit tests. These allow us to poke at internal
interfaces in ways that are difficult or impossible to do directly from
a test that lives on the other side of the API. The hope is that this
will help prevent "revealed" bugs. It's those bugs where a change in an
unrelated piece of code exposes a bug that had previously existed.
Is something like that sensible (or even possible) in the kernel?
> - Issues discovered in review and final validation need automated test
> coverage.
> The reasoning is that anything which slipped the developer's attention is
> tricky enough to warrant an explicit testcase, since in a later
> refactoring
> there's a good chance that it'll be missed again. This has a bit a risk
> to delay patches, but if the basic test coverage is good enough as per
> the previous point it really shouln't be an issue.
These are the bugs most likely to need the previously mentioned
"internal" tests. "Function X will crash in situation Y. The code that
calls X won't cause Y, but..."
> - Finally we need to push the testable frontier with new ideas like pipe
> CRCs,
> modeset state cross checking or arbitrary monitor configuration injection
> (with fixed EDIDs and connector state forcing). The point here is to
> forster
^^^^^^^ foster
> new crazy ideas, and the expectation is very much _not_ that
> developers then
> need to write testcases for all the old bugfixes that suddenly became
> testable. That workload needs to be spread out over a bunch of features
> touching the relevant area. This only really applies to features and
> code paths which are currently in the "not testable" bucket anyway.
>
> This should specify the "what" decently enough, but we also need to look
> at how
> tests should work.
>
> Specific testcases in i-g-t are obviously the preferred form, but for some
> features that's just not possible. In such cases in-kernel self-checks like
> the modeset state checker of fifo underrun reporting are really good
> approaches. Two ceaveats apply:
^^^^^^^^ caveat
> - The test infrastructure really should be orthogonal to the code being
> tested.
> In-line asserts that check for preconditions are really nice and
> useful, but
> since they're closely tied to the code itself have a good chance to be
> broken
> in the same ways.
>
> - The debug feature needs to be enabled by default, and it needs to be
> loud.
> Otherwise no one will notice that something is amiss. So currently the
> fifo
> underrun reporting doesn't really count since it only causes debug level
> output when something goes wrong. Of course it's still a really good
> tool for
> developers, just not yet for catching regressions.
>
> Finally the short lists of excuses that don't count as proper test
> coverage for
> a feature.
>
> - Manual testing. We are ridiculously limited on our QA manpower. Every
> time we
> drop something onto the "manual testing" plate something else _will_
> drop off.
> Which means in the end that we don't really have any test coverage. So
> if patches don't come with automated tests, in-kernel cross-checking or
> some other form of validation attached they need to have really good
> reasons for doing so.
>
> - Testing by product teams. The entire point of Intel OTC's "upstream
> first"
> strategy is to have a common codebase for everyone. If we break
> product trees
> every time we feed an update into them because we can't properly
> regression
> test a given feature then the value of upstreaming features is greatly
> diminished in my opinion and could potentially doom collaborations with
> product teams. We just can't have that.
>
> This means that when products teams submit patches upstream they also
> need
> to submit the relevant testcases to i-g-t.
> Intel Semiconductor AG
> Registered No. 020.30.913.786-7
> Registered Office: World Trade Center, Leutschenbachstrasse 95, 8050
> Zurich, Switzerland
>
> This e-mail and any attachments may contain confidential material for
> the sole use of the intended recipient(s). Any review or distribution by
> others is strictly prohibited. If you are not the intended recipient,
> please contact the sender and delete all copies.
>
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [RFC/Draft] Testing requirements for upstream drm/i915 patches
2013-10-30 18:11 ` Ian Romanick
@ 2013-10-30 19:05 ` Daniel Vetter
2013-10-30 20:32 ` Chad Versace
0 siblings, 1 reply; 5+ messages in thread
From: Daniel Vetter @ 2013-10-30 19:05 UTC (permalink / raw)
To: Ian Romanick
Cc: Nikkanen, Kimmo, intel-gfx, gfx-internal-devel, Hindman, Gavin,
Barnes, Jesse, Daniel Vetter, Parenteau, Paul A
On Wed, Oct 30, 2013 at 7:11 PM, Ian Romanick <idr@freedesktop.org> wrote:
>> test coverage of the existing code _before_ starting a feature instead
>> of when the patches are ready for merging should help a lot, before
>> everyone is invested into patches already and mounting rebase pain looms
>> large.
>
> This is actually an opportunity in disguise. Once you have identified
> some of the places that are really lacking coverage, you give new people
> the task to create tests for some small areas. This gives the new
> person a way to learn the code and make a contribution without hurting
> themselves.
Yeah, that would be a great way to bring up new people. The problem is
a bit that on the kernel side we have a few disadvantages compared to
mesa: We don't have a nice spec and we also don't have a fairly decent
reference implementation (the nvidia blob). So ime writing kernel
tests is much more open-ended than reading a gl extension spec and
just nocking off all the new enums and api interface points.
The other issue is that some of the bugs (especially in gem) are
ridiculously hard to reproduce. E.g. a late -rc regression in 3.11
took me a full day of head against the wall banging until I've had a
testcase for it. And that was with the bugfix already at hand and the
issue seemingly understood. A great learning experience in carefully
ordering operations and laying out objects in the gtt, but probably
not something to get started.
>> - Tests need to provide a reasonable baseline coverage of the internal
>> driver
>> state. The idea here isn't to aim for full coverage, that's an
>> impossible and
>> pointless endeavor. The goal is to have a good starting point of tests
>> so that
>> when a tricky corner case pops up in review or validation that it's not a
>> terribly big effort to add a specific testcase for it.
>
> In Mesa we've started adding tests in Mesa (run with 'make check') in
> addition to the piglit tests. These allow us to poke at internal
> interfaces in ways that are difficult or impossible to do directly from
> a test that lives on the other side of the API. The hope is that this
> will help prevent "revealed" bugs. It's those bugs where a change in an
> unrelated piece of code exposes a bug that had previously existed.
>
> Is something like that sensible (or even possible) in the kernel?
Actual unit tests are hard to impossible, since the driver (and the
kernel in general) is a spaghetti monster with complete lack of mock
objects. And often bugs happen at the interface between sw and hw, so
we need some way to inject (fake) hw events and state. I think runtime
checks otoh are really great, and especially for slow operations like
modeset the overhead doesn't matter at all.
Everywhere else where treating the kernel as a blackbox isn't good
enough we've resorted to exposing internals and special knobs through
sysfs. That includes stuff like fake hang injection, cache thrashing
or the newly added pipe CRC stuff. But it's all for runtime tests.
>> - Issues discovered in review and final validation need automated test
>> coverage.
>> The reasoning is that anything which slipped the developer's attention is
>> tricky enough to warrant an explicit testcase, since in a later
>> refactoring
>> there's a good chance that it'll be missed again. This has a bit a risk
>> to delay patches, but if the basic test coverage is good enough as per
>> the previous point it really shouln't be an issue.
>
> These are the bugs most likely to need the previously mentioned
> "internal" tests. "Function X will crash in situation Y. The code that
> calls X won't cause Y, but..."
Ime the really tricky stuff is concurrency issues.They're hard to
understand and often really hard to reproduce. We're trying though.
The other ones are bugs depending in complex ways upon the aggregate
driver state (especially for modesetting issue). Both are not easily
done as unit tests which are executed with make check.
There's also a the issue of making the kernel code compile as a
userspace executable. The usually way to solve that is to create a
loadable kernel module with all the unit tests, and there's definitely
a bit of that around already in the kernel (e.g. lockdep has a good
set of self-tests that isolate the internal lockdep state for these
tests). That approach might be useful for some parts of the i915
driver like testing the edid parser, but those tend to not be
high-priority items for testing.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [RFC/Draft] Testing requirements for upstream drm/i915 patches
2013-10-30 19:05 ` Daniel Vetter
@ 2013-10-30 20:32 ` Chad Versace
2013-11-13 13:42 ` Rodrigo Vivi
0 siblings, 1 reply; 5+ messages in thread
From: Chad Versace @ 2013-10-30 20:32 UTC (permalink / raw)
To: Daniel Vetter, Ian Romanick
Cc: Nikkanen, Kimmo, intel-gfx, gfx-internal-devel, Hindman, Gavin,
Barnes, Jesse, Daniel Vetter, Parenteau, Paul A
On 10/30/2013 12:05 PM, Daniel Vetter wrote:
> On Wed, Oct 30, 2013 at 7:11 PM, Ian Romanick <idr@freedesktop.org> wrote:
>>> test coverage of the existing code _before_ starting a feature instead
>>> of when the patches are ready for merging should help a lot, before
>>> everyone is invested into patches already and mounting rebase pain looms
>>> large.
> Yeah, that would be a great way to bring up new people. The problem is
> a bit that on the kernel side we have a few disadvantages compared to
> mesa: We don't have a nice spec and we also don't have a fairly decent
> reference implementation (the nvidia blob). So ime writing kernel
> tests is much more open-ended than reading a gl extension spec and
> just nocking off all the new enums and api interface points.
Writing *meaningful* GL tests is much more open-ended than reading a gl
spec and knocking off each item. To really test some GL features, you
must be exceedingly clever and even have an understanding of the underlying
hardware implementation to test the significant corner cases. In that
sense, it's not too different from writing a kernel test case.
My comment is intended to be positive rather than a negative correction.
The Mesa team frequently succeeds at creating good test coverage of
new GL features despite the difficulty. That fact hopefully confirms it
will be possible for the kernel team too.
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [RFC/Draft] Testing requirements for upstream drm/i915 patches
2013-10-30 20:32 ` Chad Versace
@ 2013-11-13 13:42 ` Rodrigo Vivi
0 siblings, 0 replies; 5+ messages in thread
From: Rodrigo Vivi @ 2013-11-13 13:42 UTC (permalink / raw)
To: Chad Versace
Cc: Nikkanen, Kimmo, gfx-internal-devel, Hindman, Gavin, Barnes,
Jesse, Daniel Vetter, intel-gfx, Parenteau, Paul A
I'm in favor of all Daniel said and my 2 cents here is just to
highlight how easy and straightforward is to create an intel-gpu-tools
testcase nowadays. If you know very well the feature you are
implementing you will spend couple of hours or 1 day maximum.
I agree with Daniel that it is difficult to create the test case when
you don't know exactly what is going on like when I was spending 2
days on DPMS-on-off test case that Daniel implemented in couple hours.
But anyway I felt that I learned something at least by trying it. So I
agree with Ian and Chad that this is a learning opportunity. Even
better if we maintain somewhere a list of known missing testcases or
ideas for other tests.
On Wed, Oct 30, 2013 at 6:32 PM, Chad Versace
<chad.versace@linux.intel.com> wrote:
> On 10/30/2013 12:05 PM, Daniel Vetter wrote:
>>
>> On Wed, Oct 30, 2013 at 7:11 PM, Ian Romanick <idr@freedesktop.org> wrote:
>>>>
>>>> test coverage of the existing code _before_ starting a feature
>>>> instead
>>>> of when the patches are ready for merging should help a lot, before
>>>> everyone is invested into patches already and mounting rebase pain
>>>> looms
>>>> large.
>
>
>> Yeah, that would be a great way to bring up new people. The problem is
>> a bit that on the kernel side we have a few disadvantages compared to
>> mesa: We don't have a nice spec and we also don't have a fairly decent
>> reference implementation (the nvidia blob). So ime writing kernel
>> tests is much more open-ended than reading a gl extension spec and
>> just nocking off all the new enums and api interface points.
>
>
> Writing *meaningful* GL tests is much more open-ended than reading a gl
> spec and knocking off each item. To really test some GL features, you
> must be exceedingly clever and even have an understanding of the underlying
> hardware implementation to test the significant corner cases. In that
> sense, it's not too different from writing a kernel test case.
>
> My comment is intended to be positive rather than a negative correction.
> The Mesa team frequently succeeds at creating good test coverage of
> new GL features despite the difficulty. That fact hopefully confirms it
> will be possible for the kernel team too.
>
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx
--
Rodrigo Vivi
Blog: http://blog.vivi.eng.br
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2013-11-13 13:42 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2013-10-30 16:00 [RFC/Draft] Testing requirements for upstream drm/i915 patches Daniel Vetter
2013-10-30 18:11 ` Ian Romanick
2013-10-30 19:05 ` Daniel Vetter
2013-10-30 20:32 ` Chad Versace
2013-11-13 13:42 ` Rodrigo Vivi
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