Re: [igt-dev] [PATCH i-g-t v3 4/4] tests/kms_frontbuffer_tracking: Remove redundant modesets during subtest start.

From: Paulo Zanoni <paulo.r.zanoni@intel.com>
To: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
	"igt-dev@lists.freedesktop.org" <igt-dev@lists.freedesktop.org>
Subject: Re: [igt-dev] [PATCH i-g-t v3 4/4] tests/kms_frontbuffer_tracking: Remove redundant modesets during subtest start.
Date: Thu, 05 Apr 2018 12:30:24 -0700	[thread overview]
Message-ID: <1522956624.2748.16.camel@intel.com> (raw)
In-Reply-To: <1ec07ec3-8f39-bbf2-9a3d-02746040e9b9@linux.intel.com>

Em Qui, 2018-04-05 às 21:21 +0200, Maarten Lankhorst escreveu:
> Op 05-04-18 om 18:31 schreef Paulo Zanoni:
> > Em Qua, 2018-03-21 às 12:47 -0700, Paulo Zanoni escreveu:
> > > Em Qui, 2018-03-01 às 16:33 +0100, Maarten Lankhorst escreveu:
> > > > Hey,
> > > > 
> > > > Op 27-02-18 om 09:52 schreef Maarten Lankhorst:
> > > > > CRC capturing enables the display, then disables it again.
> > > > > With
> > > > > igt_display we can use igt_display_reset to restore the
> > > > > original
> > > > > state,
> > > > > without committing it to the hw.
> > > > > 
> > > > > All subtests first set their own state anyway, so we can save
> > > > > up
> > > > > on
> > > > > the number of commits.
> > > > 
> > > > I patched igt_kms to report the number of modesets..
> > > > 
> > > > Without this patch running ./kms_frontbuffer_tracking on a 2
> > > > output
> > > > system (f2-snb-2600, forced VGA-1 enabled):
> > > > Performed 382 modesets
> > > > 
> > > > With this patch on a 2 output system:
> > > > Performed 23 modesets
> > > > 
> > > > On geminilake this means we save a lot of time, so could
> > > > someone
> > > > review this series?
> > > 
> > > Is there an analysis on how reducing the amount of modesets will
> > > *not*
> > > invalidade the purpose of the tests? The modesets are there for a
> > > reason.
> > 
> > Ping?
> 
> How will doing a modeset improve the test?
> 
> We preserve the mode only if it makes sense, each subtest sets the
> parameters it wants. It just happens that in most cases that's the
> same mode, so we don't have to do a modeset.
> That's all. :)

But having or not having a modeset, having or not having a flip changes
how the FBC code in the Kernel behaves. So changing from having a
modeset to not having one will definitely have an impact on what code
gets run. It would be good to have a detailed analysis on why this is
not the case the specific points that changed.

> 
> ~Maarten
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