From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch@lst.de>
Subject: Re: trying to understand READ_META, READ_SYNC, WRITE_SYNC & co
Date: Sat, 26 Jun 2010 12:16:13 +0200
Message-ID: <20100626101613.GA27972@lst.de>
References: <20100621110436.GA4056@lst.de> <4C1FB5F7.3070908@kernel.dk> <20100621191410.GA24213@lst.de> <20100621213618.GC6474@redhat.com> <20100623100138.GA9575@lst.de> <20100624014420.GB3297@redhat.com> <20100625110319.GA12855@lst.de> <20100626092556.GH29809@laptop> <20100626092759.GA25896@lst.de> <20100626101045.GJ29809@laptop>
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Cc: Christoph Hellwig <hch@lst.de>, Vivek Goyal <vgoyal@redhat.com>,
	Jens Axboe <axboe@kernel.dk>, linux-fsdevel@vger.kernel.org,
	linux-kernel@vger.kernel.org
To: Nick Piggin <npiggin@suse.de>
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On Sat, Jun 26, 2010 at 08:10:45PM +1000, Nick Piggin wrote:
> But I'm sure apps can submit fsyncs much faster than once per
> few ms, like small database transactions.

fsync / O_SYNC should be irrelevant for the idling logic.  One those
retourn to the user data must have made it to the disk, and with our
barrier implementation that implies fully draining any outstanding I/O
on the device.