From: yoma sophian <sophian.yoma@gmail.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: linux-mm@kvack.org
Subject: Re: some question about order0 page allocation
Date: Sun, 16 Oct 2016 19:01:23 +0800 [thread overview]
Message-ID: <CADUS3o=64pZae+Nq302RSRukCd3beRCtm3Ch=iDVkrPSUOODZw@mail.gmail.com> (raw)
In-Reply-To: <20161014152615.GB6105@dhcp22.suse.cz>
hi michal:
2016-10-14 23:26 GMT+08:00 Michal Hocko <mhocko@kernel.org>:
> On Fri 14-10-16 17:29:34, yoma sophian wrote:
> [...]
>> [ 5515.127555] dialog invoked oom-killer: gfp_mask=0x80d0, order=0,
>> oom_score_adj=0
>
> This looks like a GFP_KERNEL + something allocation
Yes, you are correct.
The page is allocated with GFP as (KERNEL + ZERO) flag
>
>> [ 5515.444859] Normal: 4314*4kB (UEMC) 3586*8kB (UMC) 131*16kB (MC)
>> 21*32kB (C) 6*64kB (C) 1*128kB (C) 0*256kB 0*512kB 0*1024kB 0*2048kB
>> 0*4096kB = 49224kB
>
> And it seems like CMA blocks are spread in all orders and no unmovable
> allocations can fallback in them. It seems that there should be some
> movable blocks but I do not have any idea why those are not used. Anyway
> this is where I would start investigating.
Per your kind hint, I trace pcp page allocation again.(since the order
of allocation is 0 this time)
I found when the list of pcp with unmovable type is empty, it will
call rmqueue_bulk for trying to get batch, 31 order-0 pages.
And rmqueue_bulk will call __rmqueue_smallest and even
__rmqueue_fallback once the buddy of unmovable memory is not enough.
But from below message:
[ 5515.444859] Normal: 4314*4kB (UEMC) 3586*8kB (UMC)
the order 0 of U type in buddy is at least has 1 page free.
That mean even there is not enough 32 order-0 pages with U in buddy
right now, buddy can at least provide 1 page to satisfy this
allocation.
if my conclusion is correct, there is no need for fallback.
Please correct me, if I am wrong.
Sincerely appreciate your kind help,
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next prev parent reply other threads:[~2016-10-16 11:01 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-14 9:29 some question about order0 page allocation yoma sophian
2016-10-14 15:26 ` Michal Hocko
2016-10-16 11:01 ` yoma sophian [this message]
2016-10-17 13:12 ` Michal Hocko
2016-10-19 7:56 ` yoma sophian
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