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 <20201217230612.32397-2-john.stultz@linaro.org> <X9y+YZujWBTHMuH3@phenom.ffwll.local>
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From:   John Stultz <john.stultz@linaro.org>
Date:   Fri, 18 Dec 2020 17:16:56 -0800
Message-ID: <CALAqxLVtYVGSSYtFmMK6oM9JSEmY4RAXra89sECL2Z4YGPic0Q@mail.gmail.com>
Subject: Re: [RFC][PATCH 2/3] dma-buf: system_heap: Add pagepool support to
 system heap
To:     John Stultz <john.stultz@linaro.org>,
        lkml <linux-kernel@vger.kernel.org>,
        Sandeep Patil <sspatil@google.com>,
        dri-devel <dri-devel@lists.freedesktop.org>,
        Ezequiel Garcia <ezequiel@collabora.com>,
        Robin Murphy <robin.murphy@arm.com>,
        James Jones <jajones@nvidia.com>,
        Liam Mark <lmark@codeaurora.org>,
        Laura Abbott <labbott@kernel.org>,
        Chris Goldsworthy <cgoldswo@codeaurora.org>,
        Hridya Valsaraju <hridya@google.com>,
        =?UTF-8?Q?=C3=98rjan_Eide?= <orjan.eide@arm.com>,
        linux-media <linux-media@vger.kernel.org>,
        Suren Baghdasaryan <surenb@google.com>,
        Daniel Mentz <danielmentz@google.com>
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On Fri, Dec 18, 2020 at 6:36 AM Daniel Vetter <daniel@ffwll.ch> wrote:
> On Thu, Dec 17, 2020 at 11:06:11PM +0000, John Stultz wrote:
> > Reuse/abuse the pagepool code from the network code to speed
> > up allocation performance.
> >
> > This is similar to the ION pagepool usage, but tries to
> > utilize generic code instead of a custom implementation.
>
> We also have one of these in ttm. I think we should have at most one of
> these for the gpu ecosystem overall, maybe as a helper that can be plugged
> into all the places.
>
> Or I'm kinda missing something, which could be since I only glanced at
> yours for a bit. But it's also called page pool for buffer allocations,
> and I don't think there's that many ways to implement that really :-)

Yea, when I was looking around the ttm one didn't seem quite as
generic as the networking one, which more easily fit in here.

The main benefit for the system heap is not so much the pool itself
(the normal page allocator is pretty good), as it being able to defer
the free and zero the pages in a background thread, so the pool is
effectively filled with pre-zeroed pages.

But I'll take another look at the ttm implementation and see if it can
be re-used or the shared code refactored and pulled out somehow.

thanks
-john