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Date: Tue, 20 Aug 2013 10:07:45 +0200 From: Stefan Priebe - Profihost AG <s.priebe@...fihost.ag> To: Kent Overstreet <kmo@...erainc.com> CC: Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org, linux-bcache@...r.kernel.org Subject: Re: bcache: Fix a writeback performance regression Am 20.08.2013 10:01, schrieb Stefan Priebe - Profihost AG: > Am 20.08.2013 00:27, schrieb Kent Overstreet: >> On Mon, Aug 19, 2013 at 12:09:24AM +0200, Stefan Priebe wrote: >>> >>> Vanilla 3.10.7 + bcache: Fix a writeback performance regression >>> >>> http://pastebin.com/raw.php?i=LXZk4cMH >> >> Whoops, at first I thought this was the same bug as one I'd already been >> chasing down that had been a harmless bug - turns out I didn't look >> closely enough at the backtrace. >> >> What happened is background writeback is deadlocking, because for some >> reason the workqueue it's running out of is a singlethreaded workqueue, >> so as soon as it decides to queue enough writeback bios that it has to >> sleep on that semaphore (which often won't happen due to the PD >> controller based ratelimiting) - boom, deadlock. >> >> Here's the fixup patch I just tested and am applying: Oh i'm now seeing very high CPU spikes of kworker... i don't see if i remove bcache: Fix a writeback performance regression. Stefan -- 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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