linux-kernel - Re: [PATCH v19 22/30] drm/shmem-helper: Add common memory shrinker

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Date: Fri, 26 Jan 2024 00:56:47 +0300
From: Dmitry Osipenko <dmitry.osipenko@...labora.com>
To: Boris Brezillon <boris.brezillon@...labora.com>
Cc: David Airlie <airlied@...il.com>, Gerd Hoffmann <kraxel@...hat.com>,
 Gurchetan Singh <gurchetansingh@...omium.org>, Chia-I Wu
 <olvaffe@...il.com>, Daniel Vetter <daniel@...ll.ch>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 Christian König <christian.koenig@....com>,
 Qiang Yu <yuq825@...il.com>, Steven Price <steven.price@....com>,
 Emma Anholt <emma@...olt.net>, Melissa Wen <mwen@...lia.com>,
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
 kernel@...labora.com, virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH v19 22/30] drm/shmem-helper: Add common memory shrinker

On 1/25/24 13:19, Boris Brezillon wrote:
> On Fri,  5 Jan 2024 21:46:16 +0300
> Dmitry Osipenko <dmitry.osipenko@...labora.com> wrote:
> 
>> +static bool drm_gem_shmem_is_evictable(struct drm_gem_shmem_object *shmem)
>> +{
>> +	return (shmem->madv >= 0) && shmem->base.funcs->evict &&
>> +		refcount_read(&shmem->pages_use_count) &&
>> +		!refcount_read(&shmem->pages_pin_count) &&
>> +		!shmem->base.dma_buf && !shmem->base.import_attach &&
>> +		!shmem->evicted;
> 
> Are we missing
> 
>                 && dma_resv_test_signaled(shmem->base.resv,
> 					  DMA_RESV_USAGE_BOOKKEEP)
> 
> to make sure the GPU is done using the BO?
> The same applies to drm_gem_shmem_is_purgeable() BTW.
> 
> If you don't want to do this test here, we need a way to let drivers
> provide a custom is_{evictable,purgeable}() test.
> 
> I guess we should also expose drm_gem_shmem_shrinker_update_lru_locked()
> to let drivers move the GEMs that were used most recently (those
> referenced by a GPU job) at the end of the evictable LRU.

We have the signaled-check in the common drm_gem_evict() helper:

https://elixir.bootlin.com/linux/v6.8-rc1/source/drivers/gpu/drm/drm_gem.c#L1496

-- 
Best regards,
Dmitry