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Message-ID: <8c5d3cb0-70fa-81a7-33a2-50f45bf8f40e@collabora.com>
Date:   Tue, 28 Jun 2022 16:11:07 +0300
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Subject: Re: [PATCH v6 00/22] Add generic memory shrinker to VirtIO-GPU and
 Panfrost DRM drivers
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To:     Robin Murphy <robin.murphy@arm.com>,
        David Airlie <airlied@linux.ie>,
        Gerd Hoffmann <kraxel@redhat.com>,
        Gurchetan Singh <gurchetansingh@chromium.org>,
        Chia-I Wu <olvaffe@gmail.com>, Daniel Vetter <daniel@ffwll.ch>,
        Daniel Almeida <daniel.almeida@collabora.com>,
        Gert Wollny <gert.wollny@collabora.com>,
        Gustavo Padovan <gustavo.padovan@collabora.com>,
        Daniel Stone <daniel@fooishbar.org>,
        Tomeu Vizoso <tomeu.vizoso@collabora.com>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Maxime Ripard <mripard@kernel.org>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        Rob Herring <robh@kernel.org>,
        Steven Price <steven.price@arm.com>,
        Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>,
        Rob Clark <robdclark@gmail.com>,
        Emil Velikov <emil.l.velikov@gmail.com>,
        Qiang Yu <yuq825@gmail.com>,
        Sumit Semwal <sumit.semwal@linaro.org>,
        =?UTF-8?Q?Christian_K=c3=b6nig?= <christian.koenig@amd.com>,
        "Pan, Xinhui" <Xinhui.Pan@amd.com>,
        Thierry Reding <thierry.reding@gmail.com>,
        Tomasz Figa <tfiga@chromium.org>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Alex Deucher <alexander.deucher@amd.com>,
        Jani Nikula <jani.nikula@linux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@intel.com>,
        Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc:     dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
        virtualization@lists.linux-foundation.org,
        Dmitry Osipenko <digetx@gmail.com>,
        linux-tegra@vger.kernel.org, linux-media@vger.kernel.org,
        linaro-mm-sig@lists.linaro.org, amd-gfx@lists.freedesktop.org,
        intel-gfx@lists.freedesktop.org, kernel@collabora.com
References: <20220526235040.678984-1-dmitry.osipenko@collabora.com>
 <49cc6f0c-e90e-8edd-52e7-4188620e2c28@arm.com>
From:   Dmitry Osipenko <dmitry.osipenko@collabora.com>
In-Reply-To: <49cc6f0c-e90e-8edd-52e7-4188620e2c28@arm.com>
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Precedence: bulk

Hello Robin,

On 6/28/22 15:31, Robin Murphy wrote:
>> Hello,
>>
>> This patchset introduces memory shrinker for the VirtIO-GPU DRM driver
>> and adds memory purging and eviction support to VirtIO-GPU driver.
>>
>> The new dma-buf locking convention is introduced here as well.
>>
>> During OOM, the shrinker will release BOs that are marked as "not needed"
>> by userspace using the new madvise IOCTL, it will also evict idling BOs
>> to SWAP. The userspace in this case is the Mesa VirGL driver, it will
>> mark
>> the cached BOs as "not needed", allowing kernel driver to release memory
>> of the cached shmem BOs on lowmem situations, preventing OOM kills.
>>
>> The Panfrost driver is switched to use generic memory shrinker.
> 
> I think we still have some outstanding issues here - Alyssa reported
> some weirdness yesterday, so I just tried provoking a low-memory
> condition locally with this series applied and a few debug options
> enabled, and the results as below were... interesting.

The warning and crash that you got actually are the minor issues.

Alyssa caught an interesting PREEMPT_DEBUG issue in the shrinker that I
haven't seen before.

She is also experiencing another problem in the Panfrost driver with a
bad shmem pages (I think). It is unrelated to this patchset and
apparently require an extra setup for the reproduction.

-- 
Best regards,
Dmitry