Re: [PATCH v2 8/8] drm/panfrost: Switch to generic memory shrinker

From: Steven Price <steven.price@arm.com>
To: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
	Gustavo Padovan <gustavo.padovan@collabora.com>,
	Daniel Stone <daniel@fooishbar.org>,
	virtualization@lists.linux-foundation.org,
	Dmitry Osipenko <digetx@gmail.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>,
	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>,
	Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Subject: Re: [PATCH v2 8/8] drm/panfrost: Switch to generic memory shrinker
Date: Fri, 18 Mar 2022 14:47:44 +0000	[thread overview]
Message-ID: <049f8b0c-7c3e-8ee1-5ae0-a4348278ee63@arm.com> (raw)
In-Reply-To: <b8d74d79-7d49-658f-5e0b-4a5da4fa2afc@collabora.com>

On 18/03/2022 14:41, Dmitry Osipenko wrote:
> 
> On 3/17/22 02:04, Dmitry Osipenko wrote:
>>
>> On 3/16/22 18:04, Steven Price wrote:
>>> On 14/03/2022 22:42, Dmitry Osipenko wrote:
>>>> Replace Panfrost's memory shrinker with a generic DRM memory shrinker.
>>>>
>>>> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
>>>> ---
>>> I gave this a spin on my Firefly-RK3288 board and everything seems to
>>> work. So feel free to add a:
>>>
>>> Tested-by: Steven Price <steven.price@arm.com>
>>>
>>> As Alyssa has already pointed out you need to remove the
>>> panfrost_gem_shrinker.c file. But otherwise everything looks fine, and
>>> I'm very happy to see the shrinker code gone ;)
>>
>> Awesome, thank you.
> 
> Steven, could you please tell me how exactly you tested the shrinker?
> 
> I realized that today's IGT doesn't have any tests for the Panfrost's
> madvise ioctl.
> 
> You may invoke "echo 2 > /proc/sys/vm/drop_caches" manually in order to
> trigger shrinker while 3d app is running actively (like a game or
> benchmark). Nothing crashing will be a good enough indicator that it
> works okay.
> 
> I may get an RK board next week and then will be able to test it by
> myself, so please don't hurry.

I have to admit it wasn't a very thorough test. I run glmark on the
board with the following hack:

diff --git a/drivers/gpu/drm/panfrost/panfrost_drv.c b/drivers/gpu/drm/panfrost/panfrost_drv.c
index b014dadcf51f..194dec00695a 100644
--- a/drivers/gpu/drm/panfrost/panfrost_drv.c
+++ b/drivers/gpu/drm/panfrost/panfrost_drv.c
@@ -279,6 +279,14 @@ static int panfrost_ioctl_submit(struct drm_device *dev, void *data,
        if (ret)
                goto out_cleanup_job;
 
+       {
+       struct shrink_control sc = {
+               .nr_to_scan = 1000
+       };
+       dev->shmem_shrinker->base.scan_objects(&dev->shmem_shrinker->base,
+                       &sc);
+       }
+
        ret = panfrost_job_push(job);
        if (ret)
                goto out_cleanup_job;

That hack was specifically because I had some doubts about the removal
of the 'gpu_usecount' counter and wanted to ensure that purging as the
job is submitted wouldn't cause problems.

The drop_caches file should also work AFAIK.

Steve
