linux-kernel - Re: [PATCH v3 0/7] dma-buf: Performance improvements for system heap & a system-uncached implementation

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Date:   Fri, 16 Oct 2020 11:47:44 -0700
From:   John Stultz <john.stultz@...aro.org>
To:     Brian Starkey <brian.starkey@....com>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Liam Mark <lmark@...eaurora.org>,
        Laura Abbott <labbott@...nel.org>,
        Hridya Valsaraju <hridya@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Sandeep Patil <sspatil@...gle.com>,
        Daniel Mentz <danielmentz@...gle.com>,
        Chris Goldsworthy <cgoldswo@...eaurora.org>,
        Ørjan Eide <orjan.eide@....com>,
        Robin Murphy <robin.murphy@....com>,
        Ezequiel Garcia <ezequiel@...labora.com>,
        Simon Ser <contact@...rsion.fr>,
        James Jones <jajones@...dia.com>,
        linux-media <linux-media@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>, nd <nd@....com>
Subject: Re: [PATCH v3 0/7] dma-buf: Performance improvements for system heap
 & a system-uncached implementation

On Thu, Oct 8, 2020 at 4:36 AM Brian Starkey <brian.starkey@....com> wrote:
>
> Hi John,
>
> On Sat, Oct 03, 2020 at 04:02:50AM +0000, John Stultz wrote:
> > Hey All,
>
> ...
>
> >
> > I did add to this series a reworked version of my uncached
> > system heap implementation I was submitting a few weeks back.
> > Since it duplicated a lot of the now reworked system heap code,
> > I realized it would be much simpler to add the functionality to
> > the system_heap implementaiton itself.
>
> That looks like a neat approach to me. Referencing your previous
> thread, I like the separate heap (as you have done), rather than a
> generic "cached"/"noncached" flag on all heaps.
>

Sounds good! I really appreciate the feedback on this.

> > While not improving the core allocation performance, the
> > uncached heap allocations do result in *much* improved
> > performance on HiKey960 as it avoids a lot of flushing and
> > invalidating buffers that the cpu doesn't touch often.
> >
> > Feedback on these would be great!
>
> Minor nit: s/detatch/detach/ on both heaps, but other than that
> you can add my r-b to patches 1-5.

Doh! Thanks for the spelling catch! Thanks again!

> As you've said, it does feel like there's some room for
> de-duplication, but that will be easier to work out once the
> implementations settle.
>
> I've a couple of comments for the uncached heap, but I'm not confident
> I understand the implications of having the non-cached alias enough to
> say if it looks OK or not.

Thanks so much!
-john