From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andi Kleen Subject: Re: cmwq and dm-crypt devices? Date: Wed, 3 Nov 2010 17:13:27 +0100 Message-ID: <20101103161327.GC18935@basil.fritz.box> References: <4BD099DB.2020108@redhat.com> <20101102220207.GD23680@redhat.com> <4CD12F6E.8040501@kernel.org> <20101103115144.GA18935@basil.fritz.box> <4CD14DF1.90601@redhat.com> <20101103123347.GB18935@basil.fritz.box> <20101103131835.GB5833@agk-dp.fab.redhat.com> 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: <20101103131835.GB5833@agk-dp.fab.redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: Andi Kleen , Milan Broz , Christophe Saout , Mike Snitzer , Brian Swetland List-Id: dm-devel.ids > Please fix this regression the patch causes then or give some > fundamental arguments why we can't satisfy the two requirements > simultaneously: I just don't understand why it is necessary to cause a > regression in stacking/low memory support in order to provide the > performance boost in the way you desire. The two things ought to be > independent of each other. The old stacking relies on per device threads. Per device threads cannot be combined with per CPU threads, because that would lead to a thread explosion for large device counts. I thought I had handled stacking, but my implementation doesn't seem to fully work. Most likely it needs a fallback thread or using one of the available workqueues. > (And I remain sceptical about the suitability of the patch even with a > stack of just two or three layers as I don't see anything in the failed > tests that shows why similar failures couldn't in principle affect Yes most likely the problem happens with any stacking > 0. -Andi -- ak@linux.intel.com -- Speaking for myself only.