Messages in this thread | | | Date | Thu, 26 Oct 2006 18:57:00 +1000 | From | David Chinner <> | Subject | Re: [PATCH] Freeze bdevs when freezing processes. |
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Hi Nigel,
On Thu, Oct 26, 2006 at 06:18:29PM +1000, Nigel Cunningham wrote: > On Thu, 2006-10-26 at 17:30 +1000, David Chinner wrote: > > We have daemons running in the background that can definitely do stuff > > after a sync. hmm - one does try_to_freeze() after a wakeup, the > > other does: > > > > if (unlikely(freezing(current))) { > > set_bit(XBT_FORCE_SLEEP, &target->bt_flags); > > refrigerator(); > > } else { > > clear_bit(XBT_FORCE_SLEEP, &target->bt_flags); > > } > > > > before it goes to sleep. So that one (xfsbufd - metadata buffer flushing) > > can definitely wake up after the sync and do work, and the other could if > > the kernel thread freeze occurs after the sync. > > > > Another good question at this point - exactly how should we be putting > > these thread to to sleep? Are both these valid methods for freezing them? > > And should we be freezing when we wake up instead of before we go to > > sleep? i.e. what are teh rules we are supposed to be following? > > As you have them at the moment, the threads seem to be freezing fine. > The issue I've seen in the past related not to threads but to timer > based activity. Admittedly it was 2.6.14 when I last looked at it, but > there used to be a possibility for XFS to submit I/O from a timer when > the threads are frozen but the bdev isn't frozen. Has that changed?
I didn't think we've ever done that - periodic or delayed operations are passed off to the kernel threads to execute. A stack trace (if you still have it) would be really help here.
Hmmm - we have a couple of per-cpu work queues as well that are used on I/O completion and that can, in some circumstances, trigger new transactions. If we are only flush metadata, then I don't think that any more I/o will be issued, but I could be wrong (maze of twisty passages).
Cheers,
Dave. -- Dave Chinner Principal Engineer SGI Australian Software Group - 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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