From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753909AbbEAPFy (ORCPT ); Fri, 1 May 2015 11:05:54 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:51842 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753502AbbEAPFw (ORCPT ); Fri, 1 May 2015 11:05:52 -0400 Date: Fri, 1 May 2015 08:05:45 -0700 From: Christoph Hellwig To: Tejun Heo Cc: Ming Lei , Christoph Hellwig , Jens Axboe , Linux Kernel Mailing List , "Justin M. Forbes" , Jeff Moyer , "v4.0" Subject: Re: [PATCH v6] block: loop: avoiding too many pending per work I/O Message-ID: <20150501150545.GA10705@infradead.org> References: <1430450881-10881-1-git-send-email-ming.lei@canonical.com> <20150501101737.GA18577@infradead.org> <20150501142221.GC1949@htj.duckdns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150501142221.GC1949@htj.duckdns.org> User-Agent: Mutt/1.5.23 (2014-03-12) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, May 01, 2015 at 10:22:21AM -0400, Tejun Heo wrote: > > > Why would you do this fall back? Shouldn't we just communicate > > > a concurrency limit to the workqueue code? > > > > It can't work with workqueue's concurrency limit because the > > queue is shared by all loop block devices, and the limit is on the > > whole queue. > > Maybe just cap max_active to NR_OF_LOOP_DEVS * 16 or sth? But idk, > how many concurrent workers are we talking about and why are we > capping per-queue concurrency from worker pool side instead of command > tag side? Also we probably should have per device workqueues to start with..