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Date: Sat, 19 Jan 2008 21:47:31 +0200 From: Török Edwin <edwintorok@...il.com> To: Arjan van de Ven <arjan@...ux.intel.com> CC: Linux Kernel <linux-kernel@...r.kernel.org> Subject: Re: [PATCH] LatencyTop: make reason (blk_execute_rq+0x7a/0xd) known Arjan van de Ven wrote: > Török Edwin wrote: >> >> Cause Maximum >> Average >> SCSI device ioctl 34.2 msec >> 14.4 msec > > great! I'll put this into my patchkit! Thanks. >> I also noticed some unsigned overflows, my top latency was sometimes a >> very large number (18................................), which >> was probably -1, or some other negative number. I haven't found a way >> to reproduce it yet (it happens very rarely). > > > I've not seen this; I'll take another peak at the code. I just captured this: Cause Maximum Average Waiting for userspace lock 18446744073638300.0 msec 9223372036783524.0 msec Waiting for processes to die (waitpid) 18446744073638296.0 msec 9223372036783520.0 msec Waiting for event (poll) 18446744073565216.0 msec 764505121372.0 msec SCSI device ioctl 35.2 msec 13.7 msec Application requested delay 19.5 msec 0.0 msec page fault 18.6 msec 4.0 msec Reading from file 16.6 msec 1.5 msec Waiting for buffer IO 15.2 msec 3.0 msec mutex lock 15.0 msec 15.0 msec I was also looking at /proc/latency_stats using watch, and I've seen that there were negative number. Unfortunately I couldn't copy+paste it, because it was gone too fast. I was running a program with 4 threads doing usleep(0) in an inf-loop. However I can't reproduce the overflow now with the same program. Best regards, --Edwin -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.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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