linux-kernel - Re: [PATCH v10 00/11] Add generic memory shrinker to VirtIO-GPU and Panfrost DRM drivers

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Message-ID: <Y+6pM/HuBuz+eqtA@phenom.ffwll.local>
Date:   Thu, 16 Feb 2023 23:07:47 +0100
From:   Daniel Vetter <daniel@...ll.ch>
To:     Dmitry Osipenko <dmitry.osipenko@...labora.com>
Cc:     Gerd Hoffmann <kraxel@...hat.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        kernel@...labora.com, virtualization@...ts.linux-foundation.org,
        David Airlie <airlied@...il.com>,
        Gurchetan Singh <gurchetansingh@...omium.org>,
        Chia-I Wu <olvaffe@...il.com>,
        Daniel Almeida <daniel.almeida@...labora.com>,
        Gustavo Padovan <gustavo.padovan@...labora.com>,
        Daniel Stone <daniel@...ishbar.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Rob Clark <robdclark@...il.com>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Christian König <christian.koenig@....com>,
        Qiang Yu <yuq825@...il.com>,
        Steven Price <steven.price@....com>,
        Alyssa Rosenzweig <alyssa.rosenzweig@...labora.com>,
        Rob Herring <robh@...nel.org>, Sean Paul <sean@...rly.run>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>
Subject: Re: [PATCH v10 00/11] Add generic memory shrinker to VirtIO-GPU and
 Panfrost DRM drivers

On Thu, Feb 16, 2023 at 11:43:38PM +0300, Dmitry Osipenko wrote:
> On 2/16/23 15:15, Daniel Vetter wrote:
> > On Mon, Jan 30, 2023 at 03:02:10PM +0300, Dmitry Osipenko wrote:
> >> On 1/27/23 11:13, Gerd Hoffmann wrote:
> >>> On Thu, Jan 26, 2023 at 01:55:09AM +0300, Dmitry Osipenko wrote:
> >>>> Hello Thomas and Gerd,
> >>>>
> >>>> On 1/9/23 00:04, Dmitry Osipenko wrote:
> >>>>> This series:
> >>>>>
> >>>>>   1. Makes minor fixes for drm_gem_lru and Panfrost
> >>>>>   2. Brings refactoring for older code
> >>>>>   3. Adds common drm-shmem memory shrinker
> >>>>>   4. Enables shrinker for VirtIO-GPU driver
> >>>>>   5. Switches Panfrost driver to the common shrinker
> >>>>>
> >>>>> Changelog:
> >>>>>
> >>>>> v10:- Rebased on a recent linux-next.
> >>>>>
> >>>>>     - Added Rob's ack to MSM "Prevent blocking within shrinker loop" patch.
> >>>>>
> >>>>>     - Added Steven's ack/r-b/t-b for the Panfrost patches.
> >>>>>
> >>>>>     - Fixed missing export of the new drm_gem_object_evict() function.
> >>>>>
> >>>>>     - Added fixes tags to the first two patches that are making minor fixes,
> >>>>>       for consistency.
> >>>>
> >>>> Do you have comments on this version? Otherwise ack will be appreciated.
> >>>> Thanks in advance!
> >>>
> >>> Don't feel like signing off on the locking changes, I'm not that
> >>> familiar with the drm locking rules.  So someone else looking at them
> >>> would be good.  Otherwise the series and specifically the virtio changes
> >>> look good to me.
> >>>
> >>> Acked-by: Gerd Hoffmann <kraxel@...hat.com>
> >>
> >> Thomas was looking at the the DRM core changes. I expect he'll ack them.
> >>
> >> Thank you for reviewing the virtio patches!
> > 
> > I think best-case would be an ack from msm people that this looks good
> > (even better a conversion for msm to start using this).
> 
> The MSM pretty much isn't touched by this patchset, apart from the minor
> common shrinker fix. Moving whole MSM to use drm_shmem should be a big
> change to the driver.
> 
> The Panfrost and VirtIO-GPU drivers already got the acks. I also tested
> the Lima driver, which uses drm-shmem helpers. Other DRM drivers should
> be unaffected by this series.

Ah that sounds good, I somehow thought that etnaviv also uses the helpers,
but there we only had problems with dma-buf. So that's all sorted.

> > Otherwise I think the locking looks reasonable, I think the tricky bits
> > have been moving the dma-buf rules, but if you want I can try to take
> > another in-depth look. But would need to be in 2 weeks since I'm going on
> > vacations, pls ping me on irc if I'm needed.
> 
> The locking conversion is mostly a straightforward replacement of mutex
> with resv lock for drm-shmem. The dma-buf rules were tricky, another
> tricky part was fixing the lockdep warning for the bogus report of
> fs_reclaim vs GEM shrinker at the GEM destroy time where I borrowed the
> drm_gem_shmem_resv_assert_held() solution from the MSM driver where Rob
> had a similar issue.

Ah I missed that detail, if msm solved that the same way then I think very
high chances it all ends up being compatible. Which is really what
matters, not so much whether every last driver actually has converted
over.

> > Otherwise would be great if we can land this soon, so that it can soak the
> > entire linux-next cycle to catch any driver specific issues.
> 
> That will be great. Was waiting for Thomas to ack the shmem patches
> since he reviewed the previous versions, but if you or anyone else could
> ack them, then will be good too. Thanks!

I'm good for an ack, but maybe ping Thomas for a review on irc since I'm
out next week. Also maybe Thomas has some series you can help land for
cross review.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch