From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx105.postini.com [74.125.245.105]) by kanga.kvack.org (Postfix) with SMTP id 586F46B003A for ; Tue, 21 May 2013 16:17:07 -0400 (EDT) Received: by mail-gh0-f170.google.com with SMTP id z10so349689ghb.29 for ; Tue, 21 May 2013 13:17:06 -0700 (PDT) Message-ID: <519BD640.4040102@gmail.com> Date: Tue, 21 May 2013 16:17:04 -0400 From: KOSAKI Motohiro MIME-Version: 1.0 Subject: Re: [RFC PATCH 02/02] swapon: add "cluster-discard" support References: <398ace0dd3ca1283372b3aad3fceeee59f6897d7.1369084886.git.aquini@redhat.com> <519AC7B3.5060902@gmail.com> <20130521102648.GB11774@x2.net.home> In-Reply-To: <20130521102648.GB11774@x2.net.home> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Karel Zak Cc: KOSAKI Motohiro , Rafael Aquini , linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, hughd@google.com, shli@kernel.org, jmoyer@redhat.com, riel@redhat.com, lwoodman@redhat.com, mgorman@suse.de (5/21/13 6:26 AM), Karel Zak wrote: > On Mon, May 20, 2013 at 09:02:43PM -0400, KOSAKI Motohiro wrote: >>> - if (fl_discard) >>> + if (fl_discard) { >>> flags |= SWAP_FLAG_DISCARD; >>> + if (fl_discard > 1) >>> + flags |= SWAP_FLAG_DISCARD_CLUSTER; >> >> This is not enough, IMHO. When running this code on old kernel, swapon() return EINVAL. >> At that time, we should fall back swapon(0x10000). > > Hmm.. currently we don't use any fallback for any swap flag (e.g. > 0x10000) for compatibility with old kernels. Maybe it's better to > keep it simple and stupid and return an error message than introduce > any super-smart semantic to hide incompatible fstab configuration. Hm. If so, I'd propose to revert the following change. > .B "\-d, \-\-discard" >-Discard freed swap pages before they are reused, if the swap >-device supports the discard or trim operation. This may improve >-performance on some Solid State Devices, but often it does not. >+Enables swap discards, if the swap device supports that, and performs >+a batch discard operation for the swap device at swapon time. And instead, I suggest to make --discard-on-swapon like the following. (better name idea is welcome) +--discard-on-swapon +Enables swap discards, if the swap device supports that, and performs +a batch discard operation for the swap device at swapon time. I mean, preserving flags semantics removes the reason we need make a fallback. -- 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