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Date: Fri, 3 Apr 2009 02:09:01 +0100 From: Matthew Garrett <mjg59@...f.ucam.org> To: david@...g.hm Cc: Nick Piggin <nickpiggin@...oo.com.au>, Theodore Tso <tytso@....edu>, Sitsofe Wheeler <sitsofe@...oo.com>, "Andreas T.Auer" <andreas.t.auer_lkml_73537@...us.ath.cx>, Alberto Gonzalez <info@...bu.es>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org> Subject: Re: Ext4 and the "30 second window of death" On Thu, Apr 02, 2009 at 05:59:53PM -0700, david@...g.hm wrote: > is laptop mode > > A. "write everything now, don't delay writes" in the hope that the drive > will be idle enough later to spin down laptop-mode doesn't delay writes. Ever. > or > > B. "delay all writes until later, then when the drive wakes up do all > pending writes at that time" so that the drive can go to sleep in the > meantime? Yes. > I've heard things in these threads that would indicate both behaviors. The code's pretty trivial. The only real functional differences laptop-mode brings are to write out all dirty pages (rather than just writing down to the watermark) and to call sys_sync() a few seconds after the last thing that hit disk rather than being satisfied from cache. It's entirely a mechanism to opportunistically take advantage of the disk being spun up. -- Matthew Garrett | mjg59@...f.ucam.org -- 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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