From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: cmwq and dm-crypt devices? Date: Wed, 03 Nov 2010 17:17:40 +0100 Message-ID: <4CD18B24.2010602@kernel.org> 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> <20101103161327.GC18935@basil.fritz.box> Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20101103161327.GC18935@basil.fritz.box> 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 Cc: Christophe Saout , Mike Snitzer , Brian Swetland , San Mehat , device-mapper development , Andrew Morton , Alasdair G Kergon , Milan Broz List-Id: dm-devel.ids Hello, On 11/03/2010 05:13 PM, Andi Kleen wrote: >> 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. Dunno the context here but creating WQ_NON_REENTRANT | WQ_MEM_RECLAIM workqueue per device should achieve what you want. It will be per-cpu while reserving only one worker per workqueue, so there won't be explosion of threads. Thanks. -- tejun