Re: [PATCH] dma-buf: system_heap: do not warn for costly allocation
From: Minchan Kim
Date: Wed Feb 10 2021 - 21:32:00 EST
On Wed, Feb 10, 2021 at 06:14:46PM -0800, John Stultz wrote:
> On Wed, Feb 10, 2021 at 3:17 PM Minchan Kim <minchan@xxxxxxxxxx> wrote:
> >
> > On Wed, Feb 10, 2021 at 01:40:02PM -0800, John Stultz wrote:
> > > On Wed, Feb 10, 2021 at 9:48 AM Minchan Kim <minchan@xxxxxxxxxx> wrote:
> > > >
> > > > On Wed, Feb 10, 2021 at 09:32:09AM -0800, John Stultz wrote:
> > > > > On Wed, Feb 10, 2021 at 8:26 AM Minchan Kim <minchan@xxxxxxxxxx> 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).
> > > > > >
> > > > > > [ 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@xxxxxxxxxx>
> > > > > > ---
> > > > > > 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]);
> > > > >
> > > > > Would it be cleaner to just set up the flags properly in the
> > > > > order_flags array? I'm not sure I understand why your patch does it
> > > > > dynamically?
> > > >
> > > > That's exactly I had in my branch for aosp fix but I wanted to
> > > > hear it explicitly from dmabuf maintainer since I was worried
> > > > chaninging order-4 allocation behavior, especially,
> > > > __GFP_NORETRY and &~__GFP_RECLAIM.
> > > > (It will make allocation failure easier than old and that's not
> > > > thing my patch is addressing).
> > >
> > > Yea. I might stick to changing just the __GFP_NOWARN.
> > >
> > > > If you want this, I am happy to change it. Shall I?
> > > >
> > > > diff --git a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/system_heap.c
> > > > index 29e49ac17251..865ec847013d 100644
> > > > --- a/drivers/dma-buf/heaps/system_heap.c
> > > > +++ b/drivers/dma-buf/heaps/system_heap.c
> > > > @@ -44,7 +44,7 @@ struct dma_heap_attachment {
> > > > | __GFP_NORETRY) & ~__GFP_RECLAIM) \
> > > > | __GFP_COMP)
> > > > #define LOW_ORDER_GFP (GFP_HIGHUSER | __GFP_ZERO | __GFP_COMP)
> > > > -static gfp_t order_flags[] = {HIGH_ORDER_GFP, LOW_ORDER_GFP, LOW_ORDER_GFP};
> > > > +static gfp_t order_flags[] = {HIGH_ORDER_GFP, HIGH_ORDER_GFP, LOW_ORDER_GFP};
> > >
> > > Maybe can you define a MID_ORDER_GFP as LOW_ORDER | __GFP_NOWARN
> > > (along with a comment in the code as to why) instead ?
> > >
> > > That avoids introducing any subtle behavioral change unintentionally.
> >
> > How about this one? Feel free to suggest better wording.
> >
> > diff --git a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/system_heap.c
> > index 29e49ac17251..6e17ff06331e 100644
> > --- a/drivers/dma-buf/heaps/system_heap.c
> > +++ b/drivers/dma-buf/heaps/system_heap.c
> > @@ -44,7 +44,13 @@ struct dma_heap_attachment {
> > | __GFP_NORETRY) & ~__GFP_RECLAIM) \
> > | __GFP_COMP)
> > #define LOW_ORDER_GFP (GFP_HIGHUSER | __GFP_ZERO | __GFP_COMP)
> > -static gfp_t order_flags[] = {HIGH_ORDER_GFP, LOW_ORDER_GFP, LOW_ORDER_GFP};
> > +/*
> > + * order-4 is PAGE_ALLOC_COSTLY_ORDER which is order allocator could fail
> > + * easier than lower orders. Since we have fallback order-0 allocation,
> > + * do not add warn.
> > + */
>
> Maybe: "Avoid warning on order-4 allocation failures as we'll fall
> back to order-0 in that case."
>
> > +#define MID_ORDER_GFP (LOW_ORDER_GFP | __GFP_NOWARN)
>
> My only other nit is to suggest sorting the LOW/MID/HIGH defines.
Yub, let me cook it
Thanks for the review, John.