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Date:   Thu, 12 Jan 2023 09:17:21 +0100
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Subject: Re: [PATCH 0/4] Track exported dma-buffers with memcg
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To:     Shakeel Butt <shakeelb@google.com>,
        "T.J. Mercier" <tjmercier@google.com>
Cc:     Tejun Heo <tj@kernel.org>, Zefan Li <lizefan.x@bytedance.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
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        =?UTF-8?Q?Arve_Hj=c3=b8nnev=c3=a5g?= <arve@android.com>,
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        Roman Gushchin <roman.gushchin@linux.dev>,
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From:   =?UTF-8?Q?Christian_K=c3=b6nig?= <christian.koenig@amd.com>
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Am 12.01.23 um 09:13 schrieb Shakeel Butt:
> On Wed, Jan 11, 2023 at 04:49:36PM -0800, T.J. Mercier wrote:
> [...]
>>> The problem is a bit that with gpu allocations reclaim is essentially "we
>>> pass the error to userspace and they get to sort the mess out". There are
>>> some exceptions (some gpu drivers to have shrinkers) would we need to make
>>> sure these shrinkers are tied into the cgroup stuff before we could enable
>>> charging for them?
>>>
>> I'm also not sure that we can depend on the dmabuf being backed at
>> export time 100% of the time? (They are for dmabuf heaps.) If not,
>> that'd make calling the existing memcg folio based functions a bit
>> difficult.
>>
> Where does the actual memory get allocated? I see the first patch is
> updating the stat in dma_buf_export() and dma_buf_release(). Does the
> memory get allocated and freed in those code paths?

Nope, dma_buf_export() just makes the memory available to others.

The driver which calls dma_buf_export() is the one allocating the memory.

Regards,
Christian.