From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail6.bemta8.messagelabs.com (mail6.bemta8.messagelabs.com [216.82.243.55]) by kanga.kvack.org (Postfix) with ESMTP id 471B86B0246 for ; Tue, 21 Jun 2011 22:42:32 -0400 (EDT) Message-ID: <4E015672.2020407@redhat.com> Date: Wed, 22 Jun 2011 10:41:54 +0800 From: Cong Wang MIME-Version: 1.0 Subject: Re: [PATCH 2/3] mm: make the threshold of enabling THP configurable References: <1308587683-2555-1-git-send-email-amwang@redhat.com> <1308587683-2555-2-git-send-email-amwang@redhat.com> <20110620165955.GB9396@suse.de> <4DFF8050.9070201@redhat.com> <20110621093640.GD9396@suse.de> In-Reply-To: <20110621093640.GD9396@suse.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Mel Gorman Cc: linux-kernel@vger.kernel.org, akpm@linux-foundation.org, Andrea Arcangeli , Mel Gorman , Benjamin Herrenschmidt , Rik van Riel , Johannes Weiner , KAMEZAWA Hiroyuki , linux-mm@kvack.org ao? 2011a1'06ae??21ae?JPY 17:36, Mel Gorman a??e??: > > Fragmentation avoidance benefits from tuning min_free_kbytes to a higher > value and minimising fragmentation-related problems is crucial if THP is > to allocate its necessary pages. > > THP tunes min_free_kbytes automatically and this value is in part > related to the number of zones. At 512M on a single node machine, the > recommended min_free_kbytes is close to 10% of memory which is barely > tolerable as it is. At 256M, it's 17%, at 128M, it's 34% so tuning the > value lower has diminishing returns as the performance impact of giving > up such a high percentage of free memory is not going to be offset by > reduced TLB misses. Tuning it to a higher value might make some sense > if the higher min_free_kbytes was a problem but it would be much more > rational to tune it as a sysctl than making it a compile-time decision. > What this patch changed is the check of total memory pages in hugepage_init(), which I don't think is suitable as a sysctl. If you mean min_free_kbytes could be tuned as a sysctl, that should be done in other patch, right? :) Thanks. -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org