oom killer and long-waiting processes
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From: Ryan Wang on 10 Jun 2010 03:20 Hi all, I have one question about oom killer: If many processes dealing with network communications, but due to bad network traffic, the processes have to wait for a very long time. And meanwhile they may consume some memeory separately for computation. The number of such processes may be large. I wonder whether oom killer will kill these processes when the system is under high pressure? thanks, -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: David Rientjes on 10 Jun 2010 16:40 On Thu, 10 Jun 2010, Ryan Wang wrote: > Hi all, > > I have one question about oom killer: > If many processes dealing with network communications, > but due to bad network traffic, the processes have to wait > for a very long time. And meanwhile they may consume > some memeory separately for computation. The number > of such processes may be large. > > I wonder whether oom killer will kill these processes > when the system is under high pressure? > The kernel can deal with "high pressure" quite well, but in some cases such as when all of your RAM or your memory controller is filled with anonymous memory and cannot be reclaimed, the oom killer may be called to kill "something". It prefers to kill something that will free a large amount of memory to avoid having to subsequently kill additional tasks when it kills something small first. If there are tasks that you'd either like to protect from the oom killer or always prefer in oom conditions, you can influence its decision-making from userspace by tuning /proc/<pid>/oom_adj of the task in question. Users typically set an oom_adj value of "-17" to completely disable oom killing of pid (the kernel will even panic if it can't find anything killable as a result of this!), a value of "-16" to prefer that pid gets killed last, and a value of "15" to always prefer pid gets killed first. Lowering a /proc/<pid>/oom_adj value for a pid from its current value (it inherits its value from the parent, which is usually 0) is only allowed by root, more specifically, it may only be done by the CAP_SYS_RESOURCE capability. You can refer to Documentation/filesystems/proc.txt for information on oom_adj. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Ryan Wang on 10 Jun 2010 20:40
2010/6/11 David Rientjes <rientjes(a)google.com>: > On Thu, 10 Jun 2010, Ryan Wang wrote: > >> Hi all, >> >> � � � � I have one question about oom killer: >> If many processes dealing with network communications, >> but due to bad network traffic, the processes have to wait >> for a very long time. And meanwhile they may consume >> some memeory separately for computation. The number >> of such processes may be large. >> >> � � � � I wonder whether oom killer will kill these processes >> when the system is under high pressure? >> > > The kernel can deal with "high pressure" quite well, but in some cases > such as when all of your RAM or your memory controller is filled with > anonymous memory and cannot be reclaimed, the oom killer may be called to > kill "something". �It prefers to kill something that will free a large > amount of memory to avoid having to subsequently kill additional tasks > when it kills something small first. > > If there are tasks that you'd either like to protect from the oom killer > or always prefer in oom conditions, you can influence its decision-making > from userspace by tuning /proc/<pid>/oom_adj of the task in question. > Users typically set an oom_adj value of "-17" to completely disable oom > killing of pid (the kernel will even panic if it can't find anything > killable as a result of this!), a value of "-16" to prefer that pid gets > killed last, and a value of "15" to always prefer pid gets killed first. > > Lowering a /proc/<pid>/oom_adj value for a pid from its current value (it > inherits its value from the parent, which is usually 0) is only allowed by > root, more specifically, it may only be done by the CAP_SYS_RESOURCE > capability. > > You can refer to Documentation/filesystems/proc.txt for information on > oom_adj. > Thanks all! -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |