Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753120Ab3C1STs (ORCPT ); Thu, 28 Mar 2013 14:19:48 -0400 Received: from userp1040.oracle.com ([156.151.31.81]:19570 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751259Ab3C1STr convert rfc822-to-8bit (ORCPT ); Thu, 28 Mar 2013 14:19:47 -0400 MIME-Version: 1.0 Message-ID: <5f1504e7-8b07-4109-8271-b214b496ca61@default> Date: Thu, 28 Mar 2013 11:19:12 -0700 (PDT) From: Dan Magenheimer To: Minchan Kim Cc: Hugh Dickins , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Seth Jennings , Nitin Gupta , Konrad Rzeszutek Wilk , Shaohua Li , Kamezawa Hiroyuki , Bob Liu Subject: RE: [RFC] mm: remove swapcache page early References: <1364350932-12853-1-git-send-email-minchan@kernel.org> <433aaa17-7547-4e39-b472-7060ee15e85f@default> <20130328010706.GB22908@blaptop> In-Reply-To: <20130328010706.GB22908@blaptop> X-Priority: 3 X-Mailer: Oracle Beehive Extensions for Outlook 2.0.1.7 (607090) [OL 12.0.6668.5000 (x86)] Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8BIT X-Source-IP: acsinet22.oracle.com [141.146.126.238] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2760 Lines: 69 > From: Minchan Kim [mailto:minchan@kernel.org] > Subject: Re: [RFC] mm: remove swapcache page early > > Hi Dan, > > On Wed, Mar 27, 2013 at 03:24:00PM -0700, Dan Magenheimer wrote: > > > From: Hugh Dickins [mailto:hughd@google.com] > > > Subject: Re: [RFC] mm: remove swapcache page early > > > > > > I believe the answer is for frontswap/zmem to invalidate the frontswap > > > copy of the page (to free up the compressed memory when possible) and > > > SetPageDirty on the PageUptodate PageSwapCache page when swapping in > > > (setting page dirty so nothing will later go to read it from the > > > unfreed location on backing swap disk, which was never written). > > > > There are two duplication issues: (1) When can the page be removed > > from the swap cache after a call to frontswap_store; and (2) When > > can the page be removed from the frontswap storage after it > > has been brought back into memory via frontswap_load. > > > > This patch from Minchan addresses (1). The issue you are raising > > No. I am addressing (2). > > > here is (2). You may not know that (2) has recently been solved > > in frontswap, at least for zcache. See frontswap_exclusive_gets_enabled. > > If this is enabled (and it is for zcache but not yet for zswap), > > what you suggest (SetPageDirty) is what happens. > > I am blind on zcache so I didn't see it. Anyway, I'd like to address it > on zram and zswap. Zswap can enable it trivially by adding a function call in init_zswap. (Note that it is not enabled by default for all frontswap backends because it is another complicated tradeoff of cpu time vs memory space that needs more study on a broad set of workloads.) I wonder if something like this would have a similar result for zram? (Completely untested... snippet stolen from swap_entry_free with SetPageDirty added... doesn't compile yet, but should give you the idea.) diff --git a/mm/page_io.c b/mm/page_io.c index 56276fe..2d10988 100644 --- a/mm/page_io.c +++ b/mm/page_io.c @@ -81,7 +81,17 @@ void end_swap_bio_read(struct bio *bio, int err) iminor(bio->bi_bdev->bd_inode), (unsigned long long)bio->bi_sector); } else { + struct swap_info_struct *sis; + SetPageUptodate(page); + sis = page_swap_info(page); + if (sis->flags & SWP_BLKDEV) { + struct gendisk *disk = sis->bdev->bd_disk; + if (disk->fops->swap_slot_free_notify) { + SetPageDirty(page); + disk->fops->swap_slot_free_notify(sis->bdev, + offset); + } + } } unlock_page(page); bio_put(bio); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/