From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [PATCH 11/11] blkcg: implement per-blkg request allocation Date: Fri, 27 Apr 2012 08:45:02 -0700 Message-ID: <20120427154502.GM27486@google.com> References: <1335477561-11131-1-git-send-email-tj@kernel.org> <1335477561-11131-12-git-send-email-tj@kernel.org> <20120427150217.GK27486@google.com> <20120427154033.GJ10579@redhat.com> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; bh=dpdxSLyXr+N25OO6v2DhAwULQ4aS4/yOtChEeWXGU2k=; b=hY2yLffJQyYlGJ/C9ON3nzV/ln4dUDScPUfi375q+d8GOYWW7aIQKq/AqwJi2WajSn 7oun2tuc6FUYawDmiPIsISY4X4UPvxvwvNuNOe4KrSgEm6UXV8DOHAmsEy/qJ2/6DhPj 5ZhoY5L+O7Tw5oNXpv7jI+PQKT3qRXVDmq/sdO07ro8yB4qZJ41oE+ZdQsd1fNAeXp6q IbtlfJG9Vo/SKLlHGnAuq1YqUZQivkCMxsg6ZWODkfoFZRajmOWtPeh9oLTkGFcNLg9w lhBMnMr7e3MEyW8VoRLZdGqEr39jJ13bV01JPSrdTJ8gKOOm3gsQxqsakY4PSv7Kjo7m R7Eg== Content-Disposition: inline In-Reply-To: <20120427154033.GJ10579-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Vivek Goyal Cc: Jeff Moyer , axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org, ctalbott-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, rni-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, fengguang.wu-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org, hughd-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org On Fri, Apr 27, 2012 at 11:40:34AM -0400, Vivek Goyal wrote: > On Fri, Apr 27, 2012 at 08:02:17AM -0700, Tejun Heo wrote: > > 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. > > So on a slow device a malicious application can easily create thousands > of group, queue up tons of IO and create unreclaimable memory easily? > Sounds little scary. Malicious application may just jack up nr_requests. Thanks. -- tejun