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Date: Tue, 8 Mar 2016 18:57:53 +0100
From: Ingo Molnar <mingo@kernel.org>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>, Wang Nan <wangnan0@huawei.com>,
        Ingo Molnar <mingo@redhat.com>, LKML <linux-kernel@vger.kernel.org>,
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        Namhyung Kim <namhyung@kernel.org>, Zefan Li <lizefan@huawei.com>,
        pi3orama@163.com
Subject: Re: [RESEND PATCH 0/5] perf core: Support overwrite ring buffer
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* Ingo Molnar <mingo@kernel.org> wrote:

> Things got a lot more lively after that!
> 
> But most of the overhead seems to come from systemd trying to dump core or 
> something like that:
> 
>  85872 mingo     20   0   34712   3016   2656 S   4.6  0.0   0:00.14 systemd-coredum                                                                                                  
>  85440 mingo     20   0   34712   3028   2664 S   4.2  0.0   0:00.13 systemd-coredum                                                                                                  
>  85751 mingo     20   0   34712   3076   2716 S   4.2  0.0   0:00.13 systemd-coredum                                                                                                  
>  85840 mingo     20   0   34712   2988   2624 S   4.2  0.0   0:00.13 systemd-coredum                                                                                                  
>  85861 mingo     20   0   34712   3080   2720 S   4.2  0.0   0:00.13 systemd-coredum                                                                                                  
>  85954 mingo     20   0   34712   3028   2664 S   4.2  0.0   0:00.13 systemd-coredum          
> 
> and I have:
> 
>  fomalhaut:~/go/src/github.com/google/syzkaller> ulimit -c
>  0
> 
> weird ... Has any of you seen such behavior?

So the workaround for that is to disable systemd trying to log every core dump to 
the system journal (!), via:

  echo > /proc/sys/kernel/core_pattern 

Thanks,

	Ingo