From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx110.postini.com [74.125.245.110]) by kanga.kvack.org (Postfix) with SMTP id 698386B00BC for ; Sun, 26 May 2013 09:52:52 -0400 (EDT) Date: Sun, 26 May 2013 10:52:37 -0300 From: Rafael Aquini Subject: Re: [PATCH 01/02] swap: discard while swapping only if SWAP_FLAG_DISCARD_PAGES Message-ID: <20130526135237.GA2333@x61.redhat.com> References: <537407790857e8a5d4db5fb294a909a61be29687.1369529143.git.aquini@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: KOSAKI Motohiro Cc: LKML , "linux-mm@kvack.org" , Andrew Morton , Hugh Dickins , shli@kernel.org, kzak@redhat.com, Jeff Moyer , "riel@redhat.com" , Larry Woodman , Mel Gorman On Sun, May 26, 2013 at 07:44:56AM -0400, KOSAKI Motohiro wrote: > > + /* > > + * By flagging sys_swapon, a sysadmin can tell us to > > + * either do sinle-time area discards only, or to just > > + * perform discards for released swap page-clusters. > > + * Now it's time to adjust the p->flags accordingly. > > + */ > > + if (swap_flags & SWAP_FLAG_DISCARD_ONCE) > > + p->flags &= ~SWP_PAGE_DISCARD; > > + else if (swap_flags & SWAP_FLAG_DISCARD_PAGES) > > + p->flags &= ~SWP_AREA_DISCARD; > > When using old swapon(8), this code turn off both flags, right? As the flag that enables swap discards SWAP_FLAG_DISCARD remains meaning the same it meant before, when using old swapon(8) (SWP_PAGE_DISCARD|SWP_AREA_DISCARD) will remain flagged when discard is enabled, so we keep doing discards the same way we did before (at swapon, and for every released page-cluster). The flags are removed orthogonally only when the new swapon(8) selects one of the particular discard policy available by using either SWAP_FLAG_DISCARD_ONCE, or SWAP_FLAG_DISCARD_PAGES flags. -- 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