Messages in this thread | | | From | Nick Piggin <> | Subject | Re: filp usage when cpu busy | Date | Thu, 1 Nov 2007 15:05:15 +1100 |
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On Thursday 01 November 2007 12:56, bc Wong (chimwong) wrote: > Hi, > > With 2.6.16 x86_64 on a 4 core machine, I noticed > that the filp usage (according to /proc/slabinfo) > shoots up and keeps on increasing sharply when one > of the CPUs is (1) locked up, or (2) very busy > doing a lot of printk()'s with KERN_EMERG. > > In the case of (1), it's permanent until it runs > out of memory eventually. For (2), it's temporary; > filp count comes back down when the printk()'s are > done. > > I can't think of any relationship between a busy/ > locked-up CPU and filp count. The system is still > functional. New short-lived processes kept being > created, but the overall number of processes is > stable. > > Does anyone know why filp count would go up like > that?
Yeah, it's probably because filp structures are freed by RCU, and if you have a locked up CPU then it can't go through a quiescent state so RCU stops freeing your filps.
If you add some cond_resched()s to your code, you should find that RCU will force a reschedule and things will work (actually, for 2.6.16, I'm not sure if RCU had the code to force a reschedule... it's force_quiescent_state() in kernel/rcupdate.c upstream). - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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