From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-la0-f46.google.com (mail-la0-f46.google.com [209.85.215.46]) by kanga.kvack.org (Postfix) with ESMTP id B86AB6B006E for ; Wed, 25 Feb 2015 11:12:05 -0500 (EST) Received: by labgf13 with SMTP id gf13so4978307lab.0 for ; Wed, 25 Feb 2015 08:12:05 -0800 (PST) Received: from mx2.suse.de (cantor2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id h2si73927279wjz.86.2015.02.25.08.12.03 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 25 Feb 2015 08:12:04 -0800 (PST) Date: Wed, 25 Feb 2015 17:11:58 +0100 From: Michal Hocko Subject: Re: [RFC v2 0/5] introduce gcma Message-ID: <20150225161158.GI26680@dhcp22.suse.cz> References: <1424721263-25314-1-git-send-email-sj38.park@gmail.com> <20150224144804.GE15626@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: SeongJae Park Cc: akpm@linux-foundation.org, lauraa@codeaurora.org, minchan@kernel.org, sergey.senozhatsky@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org On Wed 25-02-15 14:31:08, SeongJae Park wrote: > Hello Michal, > > Thanks for your comment :) > > On Tue, 24 Feb 2015, Michal Hocko wrote: > > >On Tue 24-02-15 04:54:18, SeongJae Park wrote: > >[...] > >> include/linux/cma.h | 4 + > >> include/linux/gcma.h | 64 +++ > >> mm/Kconfig | 24 + > >> mm/Makefile | 1 + > >> mm/cma.c | 113 ++++- > >> mm/gcma.c | 1321 ++++++++++++++++++++++++++++++++++++++++++++++++++ > >> 6 files changed, 1508 insertions(+), 19 deletions(-) > >> create mode 100644 include/linux/gcma.h > >> create mode 100644 mm/gcma.c > > > >Wow this is huge! And I do not see reason for it to be so big. Why > >cannot you simply define (per-cma area) 2-class users policy? Either via > >kernel command line or export areas to userspace and allow to set policy > >there. > > For implementation of the idea, we should develop not only policy selection, > but also backend for discardable memory. Most part of this patch were made > for the backend. What is the backend and why is it needed? I thought the discardable will go back to the CMA pool. I mean the cover email explained why the current CMA allocation policy might lead to lower success rate or stalls. So I would expect a new policy would be a relatively small change in the CMA allocation path to serve 2-class users as per policy. It is not clear to my why we need to pull a whole gcma layer in. I might be missing something obvious because I haven't looked at the patches yet but this should better be explained in the cover letter. Thanks! -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org