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

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Message-ID: <CAF6AEGu1_5EBmKQR8cMs=or6o_ALBWxTyKA_JL-G-AhemDyaww@mail.gmail.com>
Date:   Mon, 1 Aug 2022 13:42:33 -0700
From:   Rob Clark <robdclark@...il.com>
To:     Dmitry Osipenko <dmitry.osipenko@...labora.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 Mon, Aug 1, 2022 at 1:26 PM Dmitry Osipenko
<dmitry.osipenko@...labora.com> wrote:
>
> 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.

drm_gem_lru_move_tail_locked() is used internally, but I guess it
could be made static since there ended up not being external users
(yet?)

I could see _move_tail_locked() being useful for a driver that wanted
to bulk update a bunch of GEM objs, for ex. all the bo's associated
with a submit/job.

BR,
-R