From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch@infradead.org>
Subject: Re: Shouldn't cache=none be the default for drives?
Date: Thu, 8 Apr 2010 06:08:35 -0400
Message-ID: <20100408100835.GA29089@infradead.org>
References: <4BBC992D.3050905@gmail.com> <hpjo9m$tv8$1@dough.gmane.org> <4BBD7215.3080204@msgid.tls.msk.ru>
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Cc: Thomas Mueller <thomas@chaschperli.ch>, kvm@vger.kernel.org
To: Michael Tokarev <mjt@tls.msk.ru>
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On Thu, Apr 08, 2010 at 10:05:09AM +0400, Michael Tokarev wrote:
> LVM volumes.  This is because with cache=none, the virtual disk
> image is opened with O_DIRECT flag, which means all I/O bypasses
> host scheduler and buffer cache.

O_DIRECT does not bypass the I/O scheduler, only the page cache.