From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [PATCH v4 cgroup/for-3.7] cgroup: mark subsystems with broken hierarchy support and whine if cgroups are nested for them Date: Thu, 13 Sep 2012 13:03:54 -0700 Message-ID: <20120913200354.GN7677@google.com> References: <20120913183402.GG7677@google.com> <20120913192058.GH7677@google.com> <20120913194111.GM4396@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit 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=TC2mKHEkS2PrY6TZxJo/d0VZhJEn5mzrodHE425yDI8=; b=DJFZZfCWTYbdHMayRUfKDNFZPzH2yQ7Q2sdc+wHNj2siLDDsMDQhmFvPjWg/6st3ZL Fe5LPzv4JluDrs5kE5C3Vth/V3eucLjbDExPW0OTHd/X4f9f9ePmBnUxX8gMsg2ZhaGy aRZs60BRYwdpgqFws2RCdRj97EipQz6rls9EkYczCesPInnD1axxJ5NOhVuT9MrRl/cf 3MjaK63oIdIv/BPzcTbixk8vgL1WvAnCw1w8TQ9tdk0o+XSezpiaRq0HoBKa/i0m/FTy COSiWOjF8USmYVyxxWvPD6XLrD8oYytYucyPKBSS3qOLHPy22sJugr1Od3sXdd8UFa/j 2Zcw== Content-Disposition: inline In-Reply-To: <20120913194111.GM4396-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Vivek Goyal Cc: Neil Horman , "Serge E. Hallyn" , containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, Michal Hocko , Paul Mackerras , "Aneesh Kumar K.V" , Arnaldo Carvalho de Melo , Johannes Weiner , Thomas Graf , cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Paul Turner , Ingo Molnar Hello, Vivek. On Thu, Sep 13, 2012 at 03:41:11PM -0400, Vivek Goyal wrote: > I think for blkio controller, first level of creation itself is wrong if > hierarchy is not supported. > > root > / | \ > T1 T2 G1 > > So T1 and T2 are tasks and G1 is the created cgroup. Now if we are > expecting hierarchical controller then like cpu controller, T1, T2 and > G1 should be considered at same level and disk bandwidth should be > divided equally between T1, T2 and G1. > > But currently blkio controller looks at them as follows. > > pivot > / \ > root G1 > / \ > T1 T2 > and divides bandwidth between root and G1 equally (if weights are equal). Yeah, how to handle tasks and groups under the same cgroup is a difficult question. I don't think what blkcg does now is necessarily wrong and am not particularly fond of the idea of dealing tasks and groups as equals. It isn't clear how resource should be distributed across them - we don't have per-task knobs. I think this is a problem only for controllers which implement proportional control - cpu and blkio, am I right? Thanks. -- tejun