linux-kernel - Re: [PATCH v2] dma-buf: system_heap: use larger contiguous mappings instead of per-page mmap

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Message-ID: <CAO_48GFhmJoivvaPFFxyuA+UH9woC1JoJE4=HeKa2nmPGA53-g@mail.gmail.com>
Date: Fri, 21 Nov 2025 11:22:07 +0530
From: Sumit Semwal <sumit.semwal@...aro.org>
To: Barry Song <21cnbao@...il.com>
Cc: linaro-mm-sig@...ts.linaro.org, linux-kernel@...r.kernel.org, 
	linux-media@...r.kernel.org, Brian.Starkey@....com, 
	benjamin.gaignard@...labora.com, christian.koenig@....com, 
	dri-devel@...ts.freedesktop.org, jstultz@...gle.com, tjmercier@...gle.com, 
	v-songbaohua@...o.com, zhengtangquan@...o.com, marcin.slusarz@....com
Subject: Re: [PATCH v2] dma-buf: system_heap: use larger contiguous mappings
 instead of per-page mmap

Hi Barry,

On Fri, 21 Nov 2025 at 06:54, Barry Song <21cnbao@...il.com> wrote:
>
> Hi Sumit,
>
> >
> > Using the micro-benchmark below, we see that mmap becomes
> > 3.5X faster:
>
>
> Marcin pointed out to me off-tree that it is actually 35x faster,
> not 3.5x faster. Sorry for my poor math. I assume you can fix this
> when merging it?

Sure, I corrected this, and is merged to drm-misc-next

Thanks,
Sumit.
>
> >
> > W/ patch:
> >
> > ~ # ./a.out
> > mmap 512MB took 200266.000 us, verify OK
> > ~ # ./a.out
> > mmap 512MB took 198151.000 us, verify OK
> > ~ # ./a.out
> > mmap 512MB took 197069.000 us, verify OK
> > ~ # ./a.out
> > mmap 512MB took 196781.000 us, verify OK
> > ~ # ./a.out
> > mmap 512MB took 198102.000 us, verify OK
> > ~ # ./a.out
> > mmap 512MB took 195552.000 us, verify OK
> >
> > W/o patch:
> >
> > ~ # ./a.out
> > mmap 512MB took 6987470.000 us, verify OK
> > ~ # ./a.out
> > mmap 512MB took 6970739.000 us, verify OK
> > ~ # ./a.out
> > mmap 512MB took 6984383.000 us, verify OK
> > ~ # ./a.out
> > mmap 512MB took 6971311.000 us, verify OK
> > ~ # ./a.out
> > mmap 512MB took 6991680.000 us, verify OK
>
>
> Thanks
> Barry