linux-kernel - Re: [BUG REPORT] OOM Killer is invoked while the system still has much memory

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Date:	Tue, 14 Jul 2015 11:00:25 +0200
From:	Michal Hocko <mhocko@...nel.org>
To:	Xishi Qiu <qiuxishi@...wei.com>
Cc:	Xuzhichuang <xuzhichuang@...wei.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Songjiangtao (mygirlsjt)" <songjiangtao.song@...wei.com>,
	"Zhangwei (FF)" <zw.zhang@...wei.com>
Subject: Re: [BUG REPORT] OOM Killer is invoked while the system still has
 much memory

On Tue 14-07-15 16:42:16, Xishi Qiu wrote:
> On 2015/7/14 16:15, Michal Hocko wrote:
> 
> > On Tue 14-07-15 07:11:34, Xuzhichuang wrote:
[...]
> >> Jul 10 12:33:03 BMS_CNA04 kernel: [18136514.138968] DMA32: 188513*4kB 29459*8kB 2*16kB 2*32kB 1*64kB 0*128kB 0*256kB 1*512kB 0*1024kB 0*2048kB 0*4096kB = 990396kB
> > 
> > Moreover your allocation request was oreder 2 and you do not have much
> > memory there because most of the free memory is in order-0-2.
> > 
> 
> Hi Michal,
> 
> order=2 -> alloc 16kb memory, and DMA32 still has 2*16kB 2*32kB 1*64kB 1*512kB, 
> so you mean this large buddy block was reclaimed during the moment of oom and 
> print, right?

Not really. Those high order blocks are inaccessible for your GFP_KERNEL
allocation. See __zone_watermark_ok.

-- 
Michal Hocko
SUSE Labs
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