From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-yb0-f199.google.com (mail-yb0-f199.google.com [209.85.213.199]) by kanga.kvack.org (Postfix) with ESMTP id DF75A6B0069 for ; Thu, 1 Sep 2016 19:05:05 -0400 (EDT) Received: by mail-yb0-f199.google.com with SMTP id t65so89237688yba.0 for ; Thu, 01 Sep 2016 16:05:05 -0700 (PDT) Received: from mga09.intel.com (mga09.intel.com. [134.134.136.24]) by mx.google.com with ESMTPS id i67si7826559pfg.136.2016.09.01.16.05.04 for (version=TLS1 cipher=AES128-SHA bits=128/128); Thu, 01 Sep 2016 16:05:04 -0700 (PDT) From: "Huang\, Ying" Subject: Re: [PATCH -v2 01/10] swap: Change SWAPFILE_CLUSTER to 512 References: <1472743023-4116-1-git-send-email-ying.huang@intel.com> <1472743023-4116-2-git-send-email-ying.huang@intel.com> <20160901142246.631fe47a558bb7522f73c034@linux-foundation.org> Date: Thu, 01 Sep 2016 16:04:57 -0700 In-Reply-To: <20160901142246.631fe47a558bb7522f73c034@linux-foundation.org> (Andrew Morton's message of "Thu, 1 Sep 2016 14:22:46 -0700") Message-ID: <87h99zdxwm.fsf@yhuang-mobile.sh.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ascii Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: "Huang, Ying" , tim.c.chen@intel.com, dave.hansen@intel.com, andi.kleen@intel.com, aaron.lu@intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Hugh Dickins , Shaohua Li , Minchan Kim , Rik van Riel Andrew Morton writes: > On Thu, 1 Sep 2016 08:16:54 -0700 "Huang, Ying" wrote: > >> From: Huang Ying >> >> In this patch, the size of the swap cluster is changed to that of the >> THP (Transparent Huge Page) on x86_64 architecture (512). This is for >> the THP swap support on x86_64. Where one swap cluster will be used to >> hold the contents of each THP swapped out. And some information of the >> swapped out THP (such as compound map count) will be recorded in the >> swap_cluster_info data structure. >> >> In effect, this will enlarge swap cluster size by 2 times. Which may >> make it harder to find a free cluster when the swap space becomes >> fragmented. So that, this may reduce the continuous swap space >> allocation and sequential write in theory. The performance test in 0day >> show no regressions caused by this. >> >> --- a/mm/swapfile.c >> +++ b/mm/swapfile.c >> @@ -196,7 +196,7 @@ static void discard_swap_cluster(struct swap_info_struct *si, >> } >> } >> >> -#define SWAPFILE_CLUSTER 256 >> +#define SWAPFILE_CLUSTER 512 >> #define LATENCY_LIMIT 256 >> > > What happens to architectures which have different HPAGE_SIZE and/or > PAGE_SIZE? For the architecture with HPAGE_SIZE / PAGE_SIZE == 512 (for example x86_64), the huge page swap optimizing will be turned on. For other architectures, it will be turned off as before. This mostly because I don't know whether it is a good idea to turn on THP swap optimizing for the architectures other than x86_64. For example, it appears that the huge page size is 8M (1<<23) on SPARC. But I don't know whether 8M is too big for a swap cluster. And it appears that the huge page size could be as large as 512M on MIPS. Best Regards, Huang, Ying -- 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