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Date: Fri, 15 Feb 2013 00:53:21 +0000 From: Alasdair G Kergon <agk@...hat.com> To: Mikulas Patocka <mpatocka@...hat.com> Cc: Guangliang Zhao <gzhao@...e.com>, linux-kernel@...r.kernel.org, dm-devel@...hat.com, lucienchao@...il.com, "Alasdair G. Kergon" <agk@...hat.com> Subject: Re: [PATCH 2/2] mirror throttling On Wed, Jan 09, 2013 at 12:44:38AM -0500, Mikulas Patocka wrote: > We maintain a history of kcopyd usage in variables io_period and > total_period. The actual kcopyd activity is "(100 * io_period / > total_period)" percent of time. If we exceed user-defined percentage > threshold, we sleep. Well, I'm going to take this pair of patches for now. Some people do need this throttling today and this seems to me to be a decent and simple way to give them a lever to deal with the problem. I'm not proposing we expose this through LVM or other userspace tools at this stage: people who need it should tune it directly through sysfs. If need be, we can revisit this in future either by refining the algorithm or making it adjustable per-device rather than per-module. (Or by re-vamping kcopyd itself...) The current version is: http://people.redhat.com/agk/patches/linux/editing/dm-kcopyd-introduce-configurable-throttling.patch Alasdair -- 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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