On Mon, Sep 16, 2013 at 10:52:46PM +0200, azurIt wrote: > > CC: "Johannes Weiner" <hannes@xxxxxxxxxxx>, "Andrew Morton" <akpm@xxxxxxxxxxxxxxxxxxxx>, "David Rientjes" <rientjes@xxxxxxxxxx>, "KAMEZAWA Hiroyuki" <kamezawa.hiroyu@xxxxxxxxxxxxxx>, "KOSAKI Motohiro" <kosaki.motohiro@xxxxxxxxxxxxxx>, linux-mm@xxxxxxxxx, cgroups@xxxxxxxxxxxxxxx, x86@xxxxxxxxxx, linux-arch@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx > >On Mon 16-09-13 17:05:43, azurIt wrote: > >> > CC: "Johannes Weiner" <hannes@xxxxxxxxxxx>, "Andrew Morton" <akpm@xxxxxxxxxxxxxxxxxxxx>, "David Rientjes" <rientjes@xxxxxxxxxx>, "KAMEZAWA Hiroyuki" <kamezawa.hiroyu@xxxxxxxxxxxxxx>, "KOSAKI Motohiro" <kosaki.motohiro@xxxxxxxxxxxxxx>, linux-mm@xxxxxxxxx, cgroups@xxxxxxxxxxxxxxx, x86@xxxxxxxxxx, linux-arch@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx > >> >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. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>