From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: dm-crypt performance Date: Tue, 26 Mar 2013 02:52:29 -0400 Message-ID: <20130326065229.GA2884@infradead.org> References: Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: device-mapper development Cc: Mike Snitzer , "Alasdair G. Kergon" List-Id: dm-devel.ids On Mon, Mar 25, 2013 at 11:47:22PM -0400, Mikulas Patocka wrote: > If I sort the requests in dm-crypt to come out in the same order as they > were received, there is no longer any slowdown, the new crypt performs as > well as the old crypt, but the last time I submitted the patches, people > objected to sorting requests in dm-crypt, saying that the I/O scheduler > should sort them. But it doesn't. This problem still persists in the > current kernels. FYI, XFS also does it's own request ordering for the metadata buffers, because it knows the needed ordering and has a bigger view than than than especially CFQ. You at least have precedence in a widely used subsystem for this code.