Re: Re: [PATCH] mm: Add nr_free_highatomimic to fix incorrect watermatk routine

[Michal Hocko]

On Mon 02-09-19 13:34:54, ëìì wrote:
> >On Fri 30-08-19 18:25:53, Sangwoo wrote:
> >> The highatomic migrate block can be increased to 1% of Total memory.
> >> And, this is for only highorder ( > 0 order). So, this block size is
> >> excepted during check watermark if allocation type isn't alloc_harder.
> >>
> >> It has problem. The usage of highatomic is already calculated at
> NR_FREE_PAGES.
> >> So, if we except total block size of highatomic, it's twice minus size of
> allocated
> >> highatomic.
> >> It's cause allocation fail although free pages enough.
> >>
> >> We checked this by random test on my target(8GB RAM).
> >>
> >>  Binder:6218_2: page allocation failure: order:0, mode:0x14200ca
> (GFP_HIGHUSER_MOVABLE), nodemask=(null)
> >>  Binder:6218_2 cpuset=background mems_allowed=0
> >
> >How come this order-0 sleepable allocation fails? The upstream kernel
> >doesn't fail those allocations unless the process context is killed by
> >the oom killer.
> 
> Most calltacks are zsmalloc, as shown below.

What makes those allocations special so that they fail unlike any other
normal order-0 requests? Also do you see the same problem with the
current upstream kernel? Is it possible this is an Android specific
issue?

>  Call trace:
>   dump_backtrace+0x0/0x1f0
>   show_stack+0x18/0x20
>   dump_stack+0xc4/0x100
>   warn_alloc+0x100/0x198
>   __alloc_pages_nodemask+0x116c/0x1188
>   do_swap_page+0x10c/0x6f0
>   handle_pte_fault+0x12c/0xfe0
>   handle_mm_fault+0x1d0/0x328
>   do_page_fault+0x2a0/0x3e0
>   do_translation_fault+0x44/0xa8
>   do_mem_abort+0x4c/0xd0
>   el1_da+0x24/0x84
>   __arch_copy_to_user+0x5c/0x220
>   binder_ioctl+0x20c/0x740
>   compat_SyS_ioctl+0x128/0x248
>   __sys_trace_return+0x0/0x4
-- 
Michal Hocko
SUSE Labs