From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f200.google.com (mail-pf0-f200.google.com [209.85.192.200]) by kanga.kvack.org (Postfix) with ESMTP id A7A656B0253 for ; Fri, 22 Jul 2016 05:33:44 -0400 (EDT) Received: by mail-pf0-f200.google.com with SMTP id h186so218781585pfg.3 for ; Fri, 22 Jul 2016 02:33:44 -0700 (PDT) Received: from szxga03-in.huawei.com (szxga03-in.huawei.com. [119.145.14.66]) by mx.google.com with ESMTPS id 23si15005529pfq.32.2016.07.22.02.33.43 for (version=TLS1 cipher=AES128-SHA bits=128/128); Fri, 22 Jul 2016 02:33:43 -0700 (PDT) Message-ID: <5791E5B1.8060503@huawei.com> Date: Fri, 22 Jul 2016 17:21:53 +0800 From: Xishi Qiu MIME-Version: 1.0 Subject: Re: mm/compact: why use low watermark to determine whether compact is finished instead of use high watermark? References: <5791DFD4.5080207@huawei.com> <0b580155-d99a-f4a4-ef76-6166b41180aa@suse.cz> In-Reply-To: <0b580155-d99a-f4a4-ef76-6166b41180aa@suse.cz> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Vlastimil Babka Cc: "mel@csn.ul.ie" , David Rientjes , Joonsoo Kim , Mel Gorman , Linux MM , LKML On 2016/7/22 17:04, Vlastimil Babka wrote: > On 07/22/2016 10:56 AM, Xishi Qiu wrote: >> Hi, >> >> I find all the watermarks in mm/compaction.c are low_wmark_pages(), >> so why not use high watermark to determine whether compact is finished? > > Why would you use high watermark? Quite the opposite, I want to move towards min watermark (precisely, the one in alloc_flags which is usually min) in this series: > > https://lkml.org/lkml/2016/6/24/222 > > especially: > > https://lkml.org/lkml/2016/6/24/214 > >> e.g. >> __alloc_pages_nodemask() >> get_page_from_freelist() >> this is fast path, use use low_wmark_pages() in __zone_watermark_ok() >> >> __alloc_pages_slowpath() >> this is slow path, usually use min_wmark_pages() > > Yes, and compaction should be finished when allocation can succeed, so match __alloc_pages_slowpath(). > Sounds reasonable, but now we have kcompactd which called from kswapd, so still use low wmark? Thanks, Xishi Qiu >> >> kswapd >> balance_pgdat() >> use high_wmark_pages() to determine whether zone is balanced >> >> Thanks, >> Xishi Qiu >> > > > . > -- 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