Messages in this thread | | | Date | Fri, 28 Sep 2007 12:16:42 -0700 | From | Andrew Morton <> | Subject | Re: A unresponsive file system can hang all I/O in the system on linux-2.6.23-rc6 (dirty_thresh problem?) |
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On Fri, 28 Sep 2007 20:48:59 +0200 Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:
> > On Fri, 2007-09-28 at 11:49 -0700, Andrew Morton wrote: > > > Do you know where the stalls are occurring? throttle_vm_writeout(), or via > > direct calls to congestion_wait() from page_alloc.c and vmscan.c? (running > > sysrq-w five or ten times will probably be enough to determine this) > > would it make sense to instrument congestion_wait() callsites with > vmstats?
Better than nothing, but it isn't a great fit: we'd need one vmstat counter per congestion_wait() callsite, and it's all rather specific to the kernel-of-the-day.
taskstats delay accounting isn't useful either - it will aggregate all the schedule() callsites.
profile=sleep is just about ideal for this, isn't it? I suspect that most people don't know it's there, or forgot about it.
It could be that profile=sleep just tells us "you're spending a lot of time in io_schedule()" or congestion_wait(), so perhaps we need to teach it to go for walk up the stack somehow.
But lockdep knows how to do that already so perhaps we (ie: you ;)) can bolt sleep instrumentation onto lockdep as we (ie you ;)) did with the lockstat stuff?
(Searches for the lockstat documentation)
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