linux-kernel - Re: [PATCH v3 09/15] drm/gem: Add LRU/shrinker helper

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Date:   Mon, 1 Aug 2022 23:26:54 +0300
From:   Dmitry Osipenko <dmitry.osipenko@...labora.com>
To:     Rob Clark <robdclark@...il.com>
Cc:     dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
        linux-arm-msm@...r.kernel.org, Rob Clark <robdclark@...omium.org>,
        Daniel Vetter <daniel@...ll.ch>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        David Airlie <airlied@...ux.ie>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 09/15] drm/gem: Add LRU/shrinker helper

On 8/1/22 23:13, Dmitry Osipenko wrote:
> On 8/1/22 23:11, Dmitry Osipenko wrote:
>> On 8/1/22 23:00, Rob Clark wrote:
>>> On Mon, Aug 1, 2022 at 12:41 PM Dmitry Osipenko
>>> <dmitry.osipenko@...labora.com> wrote:
>>>>
>>>> On 7/26/22 20:50, Rob Clark wrote:
>>>>> +/**
>>>>> + * drm_gem_lru_remove - remove object from whatever LRU it is in
>>>>> + *
>>>>> + * If the object is currently in any LRU, remove it.
>>>>> + *
>>>>> + * @obj: The GEM object to remove from current LRU
>>>>> + */
>>>>> +void
>>>>> +drm_gem_lru_remove(struct drm_gem_object *obj)
>>>>> +{
>>>>> +     struct drm_gem_lru *lru = obj->lru;
>>>>> +
>>>>> +     if (!lru)
>>>>> +             return;
>>>>> +
>>>>> +     mutex_lock(lru->lock);
>>>>> +     lru_remove(obj);
>>>>> +     mutex_unlock(lru->lock);
>>>>> +}
>>>>> +EXPORT_SYMBOL(drm_gem_lru_remove);
>>>>
>>>> I made a preliminary port of the DRM-SHMEM shrinker on top of the the
>>>> latest version of dma-buf locking convention and yours LRU patches. It
>>>> all works good, the only thing that is missing for the DRM-SHMEM
>>>> shrinker is the drm_gem_lru_remove_locked().
>>>>
>>>> What about to add a locked variant of drm_gem_lru_remove()?
>>>
>>> Sounds fine to me.. the only reason it didn't exist yet was because it
>>> wasn't needed yet..
>>
>> There is no use for the drm_gem_lru_move_tail_locked() as well, you're
>> not using it in the MSM driver. Hence I thought it might be good to add
>> the drm_gem_lru_remove_locked(), or maybe the
>> drm_gem_lru_move_tail_locked() should be dropped then?
>>
>>> I can respin w/ an addition of a _locked() version, or you can add it
>>> on top in your patchset.  Either is fine by me
>>
>> The either option is fine by me too. If you'll keep the unused
>> drm_gem_lru_move_tail_locked(), then will be nice to add
>> drm_gem_lru_remove_locked().
>>
> 
> The drm_gem_lru_move_tail_locked() will be needed by DRM-SHMEM shrinker,
> BTW.

On the other hand, I see now that DRM-SHMEM shrinker can use the
unlocked versions only. Hence both drm_gem_lru_move_tail_locked() and
drm_gem_lru_remove_locked() aren't needed.

-- 
Best regards,
Dmitry