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Subject: Re: page pools, was Re: [PATCH v9 1/5] drm: Add a sharable drm
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To:     Christoph Hellwig <hch@infradead.org>,
        John Stultz <john.stultz@linaro.org>
Cc:     lkml <linux-kernel@vger.kernel.org>,
        Daniel Vetter <daniel@ffwll.ch>,
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        Laura Abbott <labbott@kernel.org>,
        Brian Starkey <Brian.Starkey@arm.com>,
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        Suren Baghdasaryan <surenb@google.com>,
        Sandeep Patil <sspatil@google.com>,
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        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>,
        Mel Gorman <mgorman@suse.de>, linux-mm <linux-mm@kvack.org>
References: <20210630013421.735092-1-john.stultz@linaro.org>
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Am 08.07.21 um 06:20 schrieb Christoph Hellwig:
> On Wed, Jul 07, 2021 at 12:35:23PM -0700, John Stultz wrote:
>> So, as Christian mentioned, on the TTM side it's useful, as they are
>> trying to avoid TLB flushes when changing caching attributes.
>>
>> For the dmabuf system heap purposes, the main benefit is moving the
>> page zeroing to the free path, rather than the allocation path. This
>> on its own doesn't save much, but allows us to defer frees (and thus
>> the zeroing) to the background, which can get that work out of the hot
>> path.
> I really do no think that is worth it to fragment the free pages.

And I think functionality like that should be part of the common page 
allocator.

I mean we already have __GFP_ZERO, why not have a background kernel 
thread which zeros free pages when a CPU core is idle? (I'm pretty sure 
we already have that somehow).

Christian.