Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759482AbcJRJ7X (ORCPT ); Tue, 18 Oct 2016 05:59:23 -0400 Received: from outbound-smtp10.blacknight.com ([46.22.139.15]:46541 "EHLO outbound-smtp10.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751963AbcJRJ7S (ORCPT ); Tue, 18 Oct 2016 05:59:18 -0400 Date: Tue, 18 Oct 2016 10:59:12 +0100 From: Mel Gorman To: zhouxianrong@huawei.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, viro@zeniv.linux.org.uk, mingo@redhat.com, peterz@infradead.org, hannes@cmpxchg.org, vbabka@suse.cz, mhocko@suse.com, vdavydov.dev@gmail.com, minchan@kernel.org, riel@redhat.com, zhouxiyu@huawei.com, zhangshiming5@huawei.com, won.ho.park@huawei.com, tuxiaobing@huawei.com Subject: Re: [PATCH] bdi flusher should not be throttled here when it fall into buddy slow path Message-ID: <20161018095912.GD22174@techsingularity.net> References: <1476774765-21130-1-git-send-email-zhouxianrong@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <1476774765-21130-1-git-send-email-zhouxianrong@huawei.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1042 Lines: 23 On Tue, Oct 18, 2016 at 03:12:45PM +0800, zhouxianrong@huawei.com wrote: > From: z00281421 > > bdi flusher may enter page alloc slow path due to writepage and kmalloc. > in that case the flusher as a direct reclaimer should not be throttled here > because it can not to reclaim clean file pages or anaonymous pages > for next moment; furthermore writeback rate of dirty pages would be > slow down and other direct reclaimers and kswapd would be affected. > bdi flusher should be iosceduled by get_request rather than here. > > Signed-off-by: z00281421 What does this patch do that PF_LESS_THROTTLE is not doing already if there is an underlying BDI? There have been a few patches like this recently that look like they might do something useful but are subtle. They really should be accompanied by a test case and data showing they either fix a functional issue (machine livelocking due to writeback not making progress) or a performance issue. -- Mel Gorman SUSE Labs