[PATCH] drm/mgag200: Enable caching for SHMEM pages

[Thomas Zimmermann]

Hi

Am 22.06.20 um 17:00 schrieb Rong Chen:
> Hi Thomas,
> 
> I tested the patch based on commit 24b806b0a1dd3, the regression

Thanks!

> of phoronix-test-suite.glmark2.1024x768.score still exists:

I expected that the test is related to drawing onto the screen. Do you
know what exactly it is testing?

Best regards
Thomas

> 
> 1f58fcaf27cb7 drm/mgag200: Enable caching for SHMEM pages                                            2 2 2
> 24b806b0a1dd3 drm-tip: 2020y-06m-22d-07h-52m-06s UTC integration manifest                            2 2 2 2 2
> 913ec479bb5cc drm/mgag200: Replace VRAM helpers with SHMEM helpers                                   2 2 2 2 2
> 88fabb75ea9ed drm/mgag200: Convert to simple KMS helper                                              165 168 167 165 164
> 
> Best Regards,
> Rong Chen
> 
> On Thu, Jun 18, 2020 at 03:34:35PM +0200, Thomas Zimmermann wrote:
>> We've had reports about performance regressions after switching
>> mgag200 from VRAM helpers to SHMEM helpers. SHMEM pages use
>> writecombine caching by default, but can also use the platform's
>> default page caching. Doing so improves the performance of I/O
>> on the framebuffer.
>>
>> Mgag200's hardware does not access framebuffer pages directly (i.e.,
>> via DMA), so enabling caching does not have an effect on consistency
>> of the framebuffer memory or the displayed data.
>>
>> Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
>> Fixes: 913ec479bb5c ("drm/mgag200: Replace VRAM helpers with SHMEM helpers")
>> Cc: Thomas Zimmermann <tzimmermann at suse.de>
>> Cc: Emil Velikov <emil.velikov at collabora.com>
>> Cc: Dave Airlie <airlied at redhat.com>
>> Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
>> Cc: Krzysztof Kozlowski <krzk at kernel.org>
>> Cc: Gerd Hoffmann <kraxel at redhat.com>
>> Cc: Sam Ravnborg <sam at ravnborg.org>
>> Cc: Rong Chen <rong.a.chen at intel.com>
>> Cc: John Donnelly <john.p.donnelly at Oracle.com>
>> Link: https://lore.kernel.org/dri-devel/20200617092252.GA5279@shao2-debian/
>> ---
>>  drivers/gpu/drm/mgag200/mgag200_drv.c | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/gpu/drm/mgag200/mgag200_drv.c b/drivers/gpu/drm/mgag200/mgag200_drv.c
>> index e19660f4a637..7189c7745baf 100644
>> --- a/drivers/gpu/drm/mgag200/mgag200_drv.c
>> +++ b/drivers/gpu/drm/mgag200/mgag200_drv.c
>> @@ -36,6 +36,7 @@ static struct drm_driver mgag200_driver = {
>>  	.major = DRIVER_MAJOR,
>>  	.minor = DRIVER_MINOR,
>>  	.patchlevel = DRIVER_PATCHLEVEL,
>> +	.gem_create_object = drm_gem_shmem_create_object_cached,
>>  	DRM_GEM_SHMEM_DRIVER_OPS,
>>  };
>>  
>> -- 
>> 2.27.0
>>

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer

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