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From:   Suren Baghdasaryan <surenb@google.com>
Date:   Wed, 10 Feb 2021 09:24:52 -0800
Message-ID: <CAJuCfpER=nbfY93CPf3Lz+bJcvAN8Vuqy6ZWZg12HnRGvznm+A@mail.gmail.com>
Subject: Re: [PATCH] dma-buf: system_heap: do not warn for costly allocation
To:     Minchan Kim <minchan@kernel.org>
Cc:     Sumit Semwal <sumit.semwal@linaro.org>,
        John Stultz <john.stultz@linaro.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Hridya Valsaraju <hridya@google.com>,
        John Dias <joaodias@google.com>
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The code looks fine to me. Description needs a bit polishing :)

On Wed, Feb 10, 2021 at 8:26 AM Minchan Kim <minchan@kernel.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:

>
> [ 1233.911533][  T460] warn_alloc: 11 callbacks suppressed
> [ 1233.911539][  T460] allocator@2.0-s: page allocation failure: order:4, mode:0x140dc2(GFP_HIGHUSER|__GFP_COMP|__GFP_ZERO), nodemask=(null),cpuset=/,mems_allowed=0
> [ 1233.926235][  T460] Call trace:
> [ 1233.929370][  T460]  dump_backtrace+0x0/0x1d8
> [ 1233.933704][  T460]  show_stack+0x18/0x24
> [ 1233.937701][  T460]  dump_stack+0xc0/0x140
> [ 1233.941783][  T460]  warn_alloc+0xf4/0x148
> [ 1233.945862][  T460]  __alloc_pages_slowpath+0x9fc/0xa10
> [ 1233.951101][  T460]  __alloc_pages_nodemask+0x278/0x2c0
> [ 1233.956285][  T460]  ion_page_pool_alloc+0xd8/0x100
> [ 1233.961144][  T460]  ion_system_heap_allocate+0xbc/0x2f0
> [ 1233.966440][  T460]  ion_buffer_create+0x68/0x274
> [ 1233.971130][  T460]  ion_buffer_alloc+0x8c/0x110
> [ 1233.975733][  T460]  ion_dmabuf_alloc+0x44/0xe8
> [ 1233.980248][  T460]  ion_ioctl+0x100/0x320
> [ 1233.984332][  T460]  __arm64_sys_ioctl+0x90/0xc8
> [ 1233.988934][  T460]  el0_svc_common+0x9c/0x168
> [ 1233.993360][  T460]  do_el0_svc+0x1c/0x28
> [ 1233.997358][  T460]  el0_sync_handler+0xd8/0x250
> [ 1234.001989][  T460]  el0_sync+0x148/0x180
>
> Signed-off-by: Minchan Kim <minchan@kernel.org>
> ---
>  drivers/dma-buf/heaps/system_heap.c | 9 +++++++--
>  1 files changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/system_heap.c
> index 29e49ac17251..33c25a5e06f9 100644
> --- a/drivers/dma-buf/heaps/system_heap.c
> +++ b/drivers/dma-buf/heaps/system_heap.c
> @@ -40,7 +40,7 @@ struct dma_heap_attachment {
>         bool mapped;
>  };
>
> -#define HIGH_ORDER_GFP  (((GFP_HIGHUSER | __GFP_ZERO | __GFP_NOWARN \
> +#define HIGH_ORDER_GFP  (((GFP_HIGHUSER | __GFP_ZERO \
>                                 | __GFP_NORETRY) & ~__GFP_RECLAIM) \
>                                 | __GFP_COMP)
>  #define LOW_ORDER_GFP (GFP_HIGHUSER | __GFP_ZERO | __GFP_COMP)
> @@ -315,6 +315,7 @@ static struct page *alloc_largest_available(unsigned long size,
>                                             unsigned int max_order)
>  {
>         struct page *page;
> +       unsigned long gfp_flags;
>         int i;
>
>         for (i = 0; i < NUM_ORDERS; i++) {
> @@ -323,7 +324,11 @@ static struct page *alloc_largest_available(unsigned long size,
>                 if (max_order < orders[i])
>                         continue;
>
> -               page = alloc_pages(order_flags[i], orders[i]);
> +               gfp_flags = order_flags[i];
> +               if (orders[i] > PAGE_ALLOC_COSTLY_ORDER)
> +                       gfp_flags |= __GFP_NOWARN;
> +
> +               page = alloc_pages(gfp_flags, orders[i]);
>                 if (!page)
>                         continue;
>                 return page;
> --
> 2.30.0.478.g8a0d178c01-goog
>