Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752527AbbLUXBW (ORCPT ); Mon, 21 Dec 2015 18:01:22 -0500 Received: from mx1.redhat.com ([209.132.183.28]:47471 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752035AbbLUXBV (ORCPT ); Mon, 21 Dec 2015 18:01:21 -0500 Date: Mon, 21 Dec 2015 15:05:58 -0200 From: Marcelo Tosatti To: Luiz Capitulino Cc: Thomas Gleixner , Fenghua Yu , "H. Peter Anvin" , Ingo Molnar , Tony Luck , Ravi V Shankar , Peter Zijlstra , Tejun Heo , linux-kernel , x86 , Vikas Shivappa Subject: Re: [PATCH V16 11/11] x86,cgroup/intel_rdt : Add a cgroup interface to manage Intel cache allocation Message-ID: <20151221170557.GA23913@amt.cnet> References: <1450392376-6397-1-git-send-email-fenghua.yu@intel.com> <1450392376-6397-12-git-send-email-fenghua.yu@intel.com> <20151220005727.GB30427@amt.cnet> <20151221104822.6d33aed0@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20151221104822.6d33aed0@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2774 Lines: 61 On Mon, Dec 21, 2015 at 10:48:22AM -0500, Luiz Capitulino wrote: > On Sat, 19 Dec 2015 22:57:30 -0200 > Marcelo Tosatti wrote: > > > On Sat, Dec 19, 2015 at 11:42:57AM +0100, Thomas Gleixner wrote: > > > On Thu, 17 Dec 2015, Fenghua Yu wrote: > > > > > > > From: Fenghua Yu > > > > > > > > From: Vikas Shivappa > > > > > > > > Add a new cgroup 'intel_rdt' to manage cache allocation. Each cgroup > > > > directory is associated with a class of service id(closid). To map a > > > > task with closid during scheduling, this patch removes the closid field > > > > from task_struct and uses the already existing 'cgroups' field in > > > > task_struct. > > > > > > > > The cgroup has a file 'l3_cbm' which represents the L3 cache capacity > > > > bitmask(CBM). The CBM is global for the whole system currently. The > > > > capacity bitmask needs to have only contiguous bits set and number of > > > > bits that can be set is less than the max bits that can be set. The > > > > tasks belonging to a cgroup get to fill in the L3 cache represented by > > > > the capacity bitmask of the cgroup. For ex: if the max bits in the CBM > > > > is 10 and the cache size is 10MB, each bit represents 1MB of cache > > > > capacity. > > > > > > > > Root cgroup always has all the bits set in the l3_cbm. User can create > > > > more cgroups with mkdir syscall. By default the child cgroups inherit > > > > the capacity bitmask(CBM) from parent. User can change the CBM specified > > > > in hex for each cgroup. Each unique bitmask is associated with a class > > > > of service ID and an -ENOSPC is returned once we run out of > > > > closids. > > > > > > This is still the original crap. No, we are not introducing this > > > interface now just because we can. I explained in great length why > > > this is completely useless and what we really need. > > > > > > Thanks, > > > > > > tglx > > > > Can you make a summary of the points, and enumerate them, please. > > (what are the problems of the current interface, and why such problems > > are fixed in the new interface?). > > Marcelo, you participated on the discussions. We discussed why this > is a bad interface a *lot* in the v15 posting. There are two writeups > that summarize all the problems: > > - https://lkml.org/lkml/2015/11/18/637 OK cool hopefully that makes it clear to Fenghua Yu what must be changed in the patchset. > - http://lkml.iu.edu/hypermail/linux/kernel/1511.0/02375.html -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/