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    SubjectRe: [patch 0/7] improve memcg oom killer robustness v2
    On Mon, Sep 16, 2013 at 10:52:46PM +0200, azurIt wrote:
    > > CC: "Johannes Weiner" <hannes@cmpxchg.org>, "Andrew Morton" <akpm@linux-foundation.org>, "David Rientjes" <rientjes@google.com>, "KAMEZAWA Hiroyuki" <kamezawa.hiroyu@jp.fujitsu.com>, "KOSAKI Motohiro" <kosaki.motohiro@jp.fujitsu.com>, linux-mm@kvack.org, cgroups@vger.kernel.org, x86@kernel.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org
    > >On Mon 16-09-13 17:05:43, azurIt wrote:
    > >> > CC: "Johannes Weiner" <hannes@cmpxchg.org>, "Andrew Morton" <akpm@linux-foundation.org>, "David Rientjes" <rientjes@google.com>, "KAMEZAWA Hiroyuki" <kamezawa.hiroyu@jp.fujitsu.com>, "KOSAKI Motohiro" <kosaki.motohiro@jp.fujitsu.com>, linux-mm@kvack.org, cgroups@vger.kernel.org, x86@kernel.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org
    > >> >On Mon 16-09-13 16:13:16, azurIt wrote:
    > >> >[...]
    > >> >> >You can use sysrq+l via serial console to see tasks hogging the CPU or
    > >> >> >sysrq+t to see all the existing tasks.
    > >> >>
    > >> >>
    > >> >> Doesn't work here, it just prints 'l' resp. 't'.
    > >> >
    > >> >I am using telnet for accessing my serial consoles exported by
    > >> >the multiplicator or KVM and it can send sysrq via ctrl+t (Send
    > >> >Break). Check your serial console setup.
    > >>
    > >>
    > >>
    > >> I'm using Raritan KVM and i created keyboard macro 'sysrq + l' resp.
    > >> 'sysrq + t'. I'm also unable to use it on my local PC. Maybe it needs
    > >> to be enabled somehow?
    > >
    > >Probably yes. echo 1 > /proc/sys/kernel/sysrq should enable all sysrq
    > >commands. You can select also some of them (have a look at
    > >Documentation/sysrq.txt for more information)
    >
    >
    > Now it happens again and i was just looking on the server's
    > htop. I'm sure that this time it was only one process (apache)
    > running under user account (not root). It was taking about 100% CPU
    > (about 100% of one core). I was able to kill it by hand inside htop
    > but everything was very slow, server load was immediately on
    > 500. I'm sure it must be related to that Johannes kernel patches
    > because i'm also using i/o throttling in cgroups via Block IO
    > controller so users are unable to create such a huge I/O. I will try
    > to take stacks of processes but i'm not able to identify the
    > problematic process so i will have to take them from *all* apache
    > processes while killing them.

    It would be fantastic if you could capture those stacks. sysrq+t
    captures ALL of them in one go and drops them into your syslog.

    /proc/<pid>/stack for individual tasks works too.


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