From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752857AbcIBUhf (ORCPT ); Fri, 2 Sep 2016 16:37:35 -0400 Received: from mga02.intel.com ([134.134.136.20]:49073 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751428AbcIBUhe (ORCPT ); Fri, 2 Sep 2016 16:37:34 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.30,272,1470726000"; d="scan'208";a="1045048049" From: "Huang\, Ying" To: Andrew Morton Cc: "Huang\, Ying" , , , , , , , Hugh Dickins , Shaohua Li , Minchan Kim , Rik van Riel 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> <87h99zdxwm.fsf@yhuang-mobile.sh.intel.com> <20160902133016.0a150c880174fa97f161912f@linux-foundation.org> Date: Fri, 02 Sep 2016 13:37:29 -0700 In-Reply-To: <20160902133016.0a150c880174fa97f161912f@linux-foundation.org> (Andrew Morton's message of "Fri, 2 Sep 2016 13:30:16 -0700") Message-ID: <87a8fqca2e.fsf@yhuang-mobile.sh.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Andrew Morton writes: > On Thu, 01 Sep 2016 16:04:57 -0700 "Huang\, Ying" wrote: > >> >> } >> >> >> >> -#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. > > This doesn't sounds very organized. If some architecture with some > config happens to have HPAGE_SIZE / PAGE_SIZE == 512 then the feature > will be turned on; otherwise it will be turned off. Nobody will even > notice that it happened. > > Would it not be better to do > > #ifdef CONFIG_SOMETHING > #define SWAPFILE_CLUSTER (HPAGE_SIZE / PAGE_SIZE) > #else > #define SWAPFILE_CLUSTER 256 > #endif > > and, by using CONFIG_SOMETHING in the other appropriate places, enable > the feature in the usual fashion? Yes. That is better. I will change it in the next version. Best Regards, Huang, Ying