From: "Christian König" <christian.koenig@amd.com>
To: John Stultz <john.stultz@linaro.org>, Daniel Vetter <daniel@ffwll.ch>
Cc: lkml <linux-kernel@vger.kernel.org>,
"Sumit Semwal" <sumit.semwal@linaro.org>,
"Liam Mark" <lmark@codeaurora.org>,
"Chris Goldsworthy" <cgoldswo@codeaurora.org>,
"Laura Abbott" <labbott@kernel.org>,
"Brian Starkey" <Brian.Starkey@arm.com>,
"Hridya Valsaraju" <hridya@google.com>,
"Suren Baghdasaryan" <surenb@google.com>,
"Sandeep Patil" <sspatil@google.com>,
"Daniel Mentz" <danielmentz@google.com>,
"Ørjan Eide" <orjan.eide@arm.com>,
"Robin Murphy" <robin.murphy@arm.com>,
"Ezequiel Garcia" <ezequiel@collabora.com>,
"Simon Ser" <contact@emersion.fr>,
"James Jones" <jajones@nvidia.com>,
linux-media <linux-media@vger.kernel.org>,
dri-devel <dri-devel@lists.freedesktop.org>
Subject: Re: [PATCH v9 1/5] drm: Add a sharable drm page-pool implementation
Date: Wed, 7 Jul 2021 08:52:12 +0200 [thread overview]
Message-ID: <f54cb539-c364-7d14-2c7c-b2b0477c125e@amd.com> (raw)
In-Reply-To: <CALAqxLVJw=0sEWxdsZ7j2QvHFDUtym3HSpkgqGdQJVayssMNeA@mail.gmail.com>
Am 06.07.21 um 23:19 schrieb John Stultz:
> On Tue, Jul 6, 2021 at 2:15 PM Daniel Vetter <daniel@ffwll.ch> wrote:
>> On Tue, Jul 6, 2021 at 11:04 PM John Stultz <john.stultz@linaro.org> wrote:
>>> On Wed, Jun 30, 2021 at 11:52 PM Christian König
>>> <christian.koenig@amd.com> wrote:
>>>> Am 01.07.21 um 00:24 schrieb John Stultz:
>>>>> On Wed, Jun 30, 2021 at 2:10 AM Christian König
>>>>> <christian.koenig@amd.com> wrote:
>>>>>> Am 30.06.21 um 03:34 schrieb John Stultz:
>>>>>>> +static unsigned long page_pool_size; /* max size of the pool */
>>>>>>> +
>>>>>>> +MODULE_PARM_DESC(page_pool_size, "Number of pages in the drm page pool");
>>>>>>> +module_param(page_pool_size, ulong, 0644);
>>>>>>> +
>>>>>>> +static atomic_long_t nr_managed_pages;
>>>>>>> +
>>>>>>> +static struct mutex shrinker_lock;
>>>>>>> +static struct list_head shrinker_list;
>>>>>>> +static struct shrinker mm_shrinker;
>>>>>>> +
>>>>>>> +/**
>>>>>>> + * drm_page_pool_set_max - Sets maximum size of all pools
>>>>>>> + *
>>>>>>> + * Sets the maximum number of pages allows in all pools.
>>>>>>> + * This can only be set once, and the first caller wins.
>>>>>>> + */
>>>>>>> +void drm_page_pool_set_max(unsigned long max)
>>>>>>> +{
>>>>>>> + if (!page_pool_size)
>>>>>>> + page_pool_size = max;
>>>>>>> +}
>>>>>>> +
>>>>>>> +/**
>>>>>>> + * drm_page_pool_get_max - Maximum size of all pools
>>>>>>> + *
>>>>>>> + * Return the maximum number of pages allows in all pools
>>>>>>> + */
>>>>>>> +unsigned long drm_page_pool_get_max(void)
>>>>>>> +{
>>>>>>> + return page_pool_size;
>>>>>>> +}
>>>>>> Well in general I don't think it is a good idea to have getters/setters
>>>>>> for one line functionality, similar applies to locking/unlocking the
>>>>>> mutex below.
>>>>>>
>>>>>> Then in this specific case what those functions do is to aid
>>>>>> initializing the general pool manager and that in turn should absolutely
>>>>>> not be exposed.
>>>>>>
>>>>>> The TTM pool manager exposes this as function because initializing the
>>>>>> pool manager is done in one part of the module and calculating the
>>>>>> default value for the pages in another one. But that is not something I
>>>>>> would like to see here.
>>>>> So, I guess I'm not quite clear on what you'd like to see...
>>>>>
>>>>> Part of what I'm balancing here is the TTM subsystem normally sets a
>>>>> global max size, whereas the old ION pool didn't have caps (instead
>>>>> just relying on the shrinker when needed).
>>>>> So I'm trying to come up with a solution that can serve both uses. So
>>>>> I've got this drm_page_pool_set_max() function to optionally set the
>>>>> maximum value, which is called in the TTM initialization path or set
>>>>> the boot argument. But for systems that use the dmabuf system heap,
>>>>> but don't use TTM, no global limit is enforced.
>>>> Yeah, exactly that's what I'm trying to prevent.
>>>>
>>>> See if we have the same functionality used by different use cases we
>>>> should not have different behavior depending on what drivers are loaded.
>>>>
>>>> Is it a problem if we restrict the ION pool to 50% of system memory as
>>>> well? If yes than I would rather drop the limit from TTM and only rely
>>>> on the shrinker there as well.
>>> Would having the default value as a config option (still overridable
>>> via boot argument) be an acceptable solution?
>> We're also trying to get ttm over to the shrinker model, and a first
>> cut of that even landed, but didn't really work out yet. So maybe just
>> aiming for the shrinker? I do agree this should be consistent across
>> the board, otherwise we're just sharing code but not actually sharing
>> functionality, which is a recipe for disaster because one side will
>> end up breaking the other side's use-case.
> Fair enough, maybe it would be best to remove the default limit, but
> leave the logic so it can still be set via the boot argument?
Yeah, that would work for me and the shrinker implementation should
already be good enough.
Regards,
Christian.
>
> thanks
> -john
next prev parent reply other threads:[~2021-07-07 6:52 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-30 1:34 [PATCH v9 0/5] Generic page pool & deferred freeing for system dmabuf hea John Stultz
2021-06-30 1:34 ` [PATCH v9 1/5] drm: Add a sharable drm page-pool implementation John Stultz
2021-06-30 9:10 ` Christian König
2021-06-30 22:24 ` John Stultz
2021-07-01 6:52 ` Christian König
2021-07-06 21:03 ` John Stultz
2021-07-06 21:15 ` Daniel Vetter
2021-07-06 21:19 ` John Stultz
2021-07-07 6:52 ` Christian König [this message]
2021-07-07 6:38 ` page pools, was " Christoph Hellwig
2021-07-07 7:10 ` Christian König
2021-07-07 7:14 ` Christoph Hellwig
2021-07-07 9:32 ` Christian König
2021-07-07 19:42 ` John Stultz
2021-07-07 19:35 ` John Stultz
2021-07-08 4:20 ` Christoph Hellwig
2021-07-08 7:37 ` Christian König
2021-06-30 1:34 ` [PATCH v9 2/5] drm: ttm_pool: Rework ttm_pool to use drm_page_pool John Stultz
2021-06-30 5:11 ` kernel test robot
2021-06-30 1:34 ` [PATCH v9 3/5] dma-buf: system_heap: Add drm pagepool support to system heap John Stultz
2021-06-30 4:34 ` kernel test robot
2021-06-30 5:25 ` kernel test robot
2021-06-30 1:34 ` [PATCH v9 4/5] dma-buf: heaps: Add deferred-free-helper library code John Stultz
2021-06-30 1:34 ` [PATCH v9 5/5] dma-buf: system_heap: Add deferred freeing to the system heap John Stultz
2021-06-30 9:13 ` [PATCH v9 0/5] Generic page pool & deferred freeing for system dmabuf hea Christian König
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