[Intel-gfx] sna: Experimental support for write-combining mmaps (wc-mmap)

[Sedat Dilek]

On Fri, Nov 7, 2014 at 11:29 AM, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> On Fri, Nov 07, 2014 at 11:08:41AM +0100, Sedat Dilek wrote:
>> Hi,
>>
>> I am playing with wc-mmap [1]... (and sent a trivial patch [0]).
>>
>> Inspecting my logs...
>>
>> $ egrep 'wc|mmap'
>> logs/build-and-install-log_XF86-Video-Intel-v2-99-916-137-g0aa2edb_WCMMAP_llvm-3-4-2.txt
>>   Experimental support: TearFree mmap(wc)
>>
>> $ egrep -i 'wc|mmap|write|comb' /var/log/Xorg.0.log
>> [ EMPTY ]
>>
>> TearFree [1] can be set via an option in xorg.conf.
>> Doing a very quick look into the sources, such a flag/option is not recognized.
>>
>> How do I see if wc-mmap is enabled/active on my desktop?
>
> Er, hopefully you don't notice anything except it speeds up certain
> operations (quite considerably) :). You have to enable the DBG output to
> see it in action, as it is quite a lowlevel feature (i.e. how we
> interact with the kernel) and should not add any user visible features.
> However, it does also require the kernel patch for it to be enabled.

Can you point me to that kernel-patch?
Is Linux v3.18-rc2+ good enough or do I need d-i-l-n / d-i-n?

- Sedat -