From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760409Ab2D0PCZ (ORCPT ); Fri, 27 Apr 2012 11:02:25 -0400 Received: from mail-pb0-f46.google.com ([209.85.160.46]:35151 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760391Ab2D0PCX (ORCPT ); Fri, 27 Apr 2012 11:02:23 -0400 Date: Fri, 27 Apr 2012 08:02:17 -0700 From: Tejun Heo To: Jeff Moyer Cc: axboe@kernel.dk, vgoyal@redhat.com, ctalbott@google.com, rni@google.com, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, containers@lists.linux-foundation.org, fengguang.wu@intel.com, hughd@google.com, akpm@linux-foundation.org Subject: Re: [PATCH 11/11] blkcg: implement per-blkg request allocation Message-ID: <20120427150217.GK27486@google.com> References: <1335477561-11131-1-git-send-email-tj@kernel.org> <1335477561-11131-12-git-send-email-tj@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On Fri, Apr 27, 2012 at 10:54:01AM -0400, Jeff Moyer wrote: > > This patch implements per-blkg request_list. Each blkg has its own > > request_list and any IO allocates its request from the matching blkg > > making blkcgs completely isolated in terms of request allocation. > > So, nr_requests is now actually nr_requests * # of blk cgroups. Is that > right? Are you at all concerned about the amount of memory that can be > tied up as the number of cgroups increases? Yeah, I thought about it and I don't think there's a single good solution here. The other extreme would be splitting nr_requests by the number of cgroups but that seems even worse - each cgroup should be able to hit maximum throughput. Given that a lot of workloads tend to regulate themselves before hitting nr_requests, I think it's best to leave it as-is and treat each cgroup as having separate channel for now. It's a configurable parameter after all. Thanks. -- tejun