netdev - Re: [PATCH] igb: don't reuse pages with pfmemalloc flag

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Message-Id: <4321414050723@webcorp02h.yandex-team.ru>
Date:	Thu, 23 Oct 2014 11:52:03 +0400
From:	Roman Gushchin <klamm@...dex-team.ru>
To:	Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Cc:	"jesse.brandeburg@...el.com" <jesse.brandeburg@...el.com>,
	"bruce.w.allan@...el.com" <bruce.w.allan@...el.com>,
	"carolyn.wyborny@...el.com" <carolyn.wyborny@...el.com>,
	"donald.c.skidmore@...el.com" <donald.c.skidmore@...el.com>,
	"gregory.v.rose@...el.com" <gregory.v.rose@...el.com>,
	"peter.p.waskiewicz.jr@...el.com" <peter.p.waskiewicz.jr@...el.com>,
	"alexander.h.duyck@...el.com" <alexander.h.duyck@...el.com>,
	"john.ronciak@...el.com" <john.ronciak@...el.com>,
	"tushar.n.dave@...el.com" <tushar.n.dave@...el.com>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"sassmann@...nic.de" <sassmann@...nic.de>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"e1000-devel@...ts.sourceforge.net" 
	<e1000-devel@...ts.sourceforge.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] igb: don't reuse pages with pfmemalloc flag

Thank you!

Probably we should add it to stable trees too?

--
Regards,
Roman

22.10.2014, 22:30, "Jeff Kirsher" <jeffrey.t.kirsher@...el.com>:
> On Wed, 2014-10-22 at 17:50 +0400, Roman Gushchin wrote:
>>  Incoming packet is dropped silently by sk_filter(), if the skb was
>>  allocated from pfmemalloc reserves and the corresponding socket is
>>  not marked with the SOCK_MEMALLOC flag.
>>
>>  Igb driver allocates pages for DMA with __skb_alloc_page(), which
>>  calls alloc_pages_node() with the __GFP_MEMALLOC flag. So, in case
>>  of OOM condition, igb can get pages with pfmemalloc flag set.
>>
>>  If an incoming packet hits the pfmemalloc page and is large enough
>>  (small packets are copying into the memory, allocated with
>>  netdev_alloc_skb_ip_align(), so they are not affected), it will be
>>  dropped.
>>
>>  This behavior is ok under high memory pressure, but the problem is
>>  that the igb driver reuses these mapped pages. So, packets are still
>>  dropping even if all memory issues are gone and there is a plenty
>>  of free memory.
>>
>>  In my case, some TCP sessions hang on a small percentage (< 0.1%)
>>  of machines days after OOMs.
>>
>>  Fix this by avoiding reuse of such pages.
>>
>>  Signed-off-by: Roman Gushchin <klamm@...dex-team.ru>
>>  ---
>>   drivers/net/ethernet/intel/igb/igb_main.c | 6 +++++-
>>   1 file changed, 5 insertions(+), 1 deletion(-)
>
> Thanks Roman, I have added you patch to my queue.
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