linux-kernel - Re: [PATCH] dma-buf: system_heap: do not warn for costly allocation

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Message-ID: <YCQaxiaiJ8Ps8IkB@google.com>
Date:   Wed, 10 Feb 2021 09:41:26 -0800
From:   Minchan Kim <minchan@...nel.org>
To:     Suren Baghdasaryan <surenb@...gle.com>
Cc:     Sumit Semwal <sumit.semwal@...aro.org>,
        John Stultz <john.stultz@...aro.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Hridya Valsaraju <hridya@...gle.com>,
        John Dias <joaodias@...gle.com>
Subject: Re: [PATCH] dma-buf: system_heap: do not warn for costly allocation

On Wed, Feb 10, 2021 at 09:24:52AM -0800, Suren Baghdasaryan wrote:
> The code looks fine to me. Description needs a bit polishing :)
> 
> On Wed, Feb 10, 2021 at 8:26 AM Minchan Kim <minchan@...nel.org> wrote:
> >
> > Linux VM is not hard to support PAGE_ALLOC_COSTLY_ODER allocation
> > so normally expects driver passes __GFP_NOWARN in that case
> > if they has fallback options.
> >
> > system_heap in dmabuf is the case so do not flood into demsg
> > with the warning for recording more precious information logs.
> > (below is ION warning example I got but dmabuf system heap is
> > nothing different).
> 
> Suggestion:
> Dmabuf system_heap allocation logic starts with the highest necessary
> allocation order before falling back to lower orders. The requested
> order can be higher than PAGE_ALLOC_COSTLY_ODER and failures to
> allocate will flood dmesg with warnings. Such high-order allocations
> are not unexpected and are handled by the system_heap's allocation
> fallback mechanism.
> Prevent these warnings when allocating higher than
> PAGE_ALLOC_COSTLY_ODER pages using __GFP_NOWARN flag.
> 
> Below is ION warning example I got but dmabuf system heap is nothing different:

I will take it.
Thanks, Suren!