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From: Qian Cai <cai@lca.pw>
To: Eric Dumazet <eric.dumazet@gmail.com>, davem@davemloft.net
Cc: netdev@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] net/skbuff: silence warnings under memory pressure
Date: Fri, 30 Aug 2019 11:25:28 -0400	[thread overview]
Message-ID: <1567178728.5576.32.camel@lca.pw> (raw)
In-Reply-To: <6109dab4-4061-8fee-96ac-320adf94e130@gmail.com>

On Fri, 2019-08-30 at 17:11 +0200, Eric Dumazet wrote:
> 
> On 8/30/19 4:57 PM, Qian Cai wrote:
> > When running heavy memory pressure workloads, the system is throwing
> > endless warnings below due to the allocation could fail from
> > __build_skb(), and the volume of this call could be huge which may
> > generate a lot of serial console output and cosumes all CPUs as
> > warn_alloc() could be expensive by calling dump_stack() and then
> > show_mem().
> > 
> > Fix it by silencing the warning in this call site. Also, it seems
> > unnecessary to even print a warning at all if the allocation failed in
> > __build_skb(), as it may just retransmit the packet and retry.
> > 
> 
> Same patches are showing up there and there from time to time.
> 
> Why is this particular spot interesting, against all others not adding
> __GFP_NOWARN ?
> 
> Are we going to have hundred of patches adding __GFP_NOWARN at various points,
> or should we get something generic to not flood the syslog in case of memory
> pressure ?
> 

From my testing which uses LTP oom* tests. There are only 3 places need to be
patched. The other two are in IOMMU code for both Intel and AMD. The place is
particular interesting because it could cause the system with floating serial
console output for days without making progress in OOM. I suppose it ends up in
a looping condition that warn_alloc() would end up generating more calls into
__build_skb() via ksoftirqd.

  reply	other threads:[~2019-08-30 15:25 UTC|newest]

Thread overview: 51+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-30 14:57 [PATCH] net/skbuff: silence warnings under memory pressure Qian Cai
2019-08-30 15:11 ` Eric Dumazet
2019-08-30 15:25   ` Qian Cai [this message]
2019-08-30 16:15     ` Eric Dumazet
2019-08-30 18:06       ` Qian Cai
2019-09-03 13:22       ` Michal Hocko
2019-09-03 15:42         ` Qian Cai
2019-09-03 18:53           ` Michal Hocko
2019-09-03 21:42             ` Qian Cai
2019-09-04  6:15               ` Michal Hocko
2019-09-04  6:41                 ` Sergey Senozhatsky
2019-09-04  6:54                   ` Michal Hocko
2019-09-04  7:19                     ` Sergey Senozhatsky
2019-09-04  7:43                       ` Sergey Senozhatsky
2019-09-04 12:14                         ` Qian Cai
2019-09-04 14:48                           ` Sergey Senozhatsky
2019-09-04 15:07                             ` Qian Cai
2019-09-04 20:42                             ` Qian Cai
2019-09-05  8:32                               ` Eric Dumazet
2019-09-05 14:09                                 ` Qian Cai
2019-09-05 15:06                                   ` Eric Dumazet
2019-09-05 15:14                                   ` Eric Dumazet
2019-09-05 11:32                               ` Sergey Senozhatsky
2019-09-05 16:03                                 ` Qian Cai
2019-09-05 17:14                                   ` Steven Rostedt
2019-09-06  2:50                                     ` Sergey Senozhatsky
2019-09-06  4:32                                   ` Sergey Senozhatsky
2019-09-06 21:17                                     ` Qian Cai
2019-09-05 17:23                                 ` Steven Rostedt
2019-09-06  3:39                                   ` Sergey Senozhatsky
2019-09-06 15:32                                     ` Petr Mladek
2019-09-09  1:10                                       ` Sergey Senozhatsky
2019-09-06 14:55                                 ` Petr Mladek
2019-09-06 19:51                                   ` Sergey Senozhatsky
2019-11-14 17:12                                 ` Qian Cai
2019-11-18 15:27                                   ` Petr Mladek
2019-11-19  0:41                                     ` Sergey Senozhatsky
2019-11-19  9:41                                       ` Petr Mladek
2019-11-19 15:58                                         ` Qian Cai
2019-11-20  1:30                                         ` Sergey Senozhatsky
2019-11-20 16:13                                           ` Petr Mladek
2019-11-21  1:05                                             ` Sergey Senozhatsky
2019-11-21  9:15                                               ` Petr Mladek
2019-09-04  7:00                   ` Sergey Senozhatsky
2019-09-04  8:25                     ` Michal Hocko
2019-09-04 11:59                       ` Qian Cai
2019-09-04 12:07                         ` Michal Hocko
2019-09-04 12:28                           ` Qian Cai
2019-09-07 11:00                       ` Tetsuo Handa
2019-09-04  6:15               ` Michal Hocko
2019-09-02 14:24     ` Vlastimil Babka

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