Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752772Ab3EIUPr (ORCPT ); Thu, 9 May 2013 16:15:47 -0400 Received: from mail-ve0-f180.google.com ([209.85.128.180]:36410 "EHLO mail-ve0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752238Ab3EIUPq (ORCPT ); Thu, 9 May 2013 16:15:46 -0400 Date: Thu, 9 May 2013 16:15:42 -0400 From: Konrad Rzeszutek Wilk To: Minchan Kim Cc: Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Hugh Dickins , Seth Jennings , Nitin Gupta , Shaohua Li , Dan Magenheimer Subject: Re: [PATCH v3] mm: remove compressed copy from zram in-memory Message-ID: <20130509201540.GB5273@localhost.localdomain> References: <1368056517-31065-1-git-send-email-minchan@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1368056517-31065-1-git-send-email-minchan@kernel.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4231 Lines: 124 On Thu, May 09, 2013 at 08:41:57AM +0900, Minchan Kim wrote: Hey Michan, Just a couple of syntax corrections. The code comment could also benefit from this. Otherwise it looks OK to me. > Swap subsystem does lazy swap slot free with expecting the page ^-a ^- the expectation that > would be swapped out again so we can avoid unnecessary write. ^--that it > > But the problem in in-memory swap(ex, zram) is that it consumes ^^-with > memory space until vm_swap_full(ie, used half of all of swap device) > condition meet. It could be bad if we use multiple swap device, ^- 'is' ^^^^^ - 'would' ^^^^^-devices > small in-memory swap and big storage swap or in-memory swap alone. ^-, ^-, > > This patch makes swap subsystem free swap slot as soon as swap-read > is completed and make the swapcache page dirty so the page should ^-makes ^-'that the' > be written out the swap device to reclaim it. > It means we never lose it. > > I tested this patch with kernel compile workload. ^-a > > 1. before > > compile time : 9882.42 > zram max wasted space by fragmentation: 13471881 byte > memory space consumed by zram: 174227456 byte > the number of slot free notify: 206684 > > 2. after > > compile time : 9653.90 > zram max wasted space by fragmentation: 11805932 byte > memory space consumed by zram: 154001408 byte > the number of slot free notify: 426972 > > * changelog from v3 > * Rebased on next-20130508 > > * changelog from v1 > * Add more comment > > Cc: Hugh Dickins > Cc: Seth Jennings > Cc: Nitin Gupta > Cc: Konrad Rzeszutek Wilk > Cc: Shaohua Li > Signed-off-by: Dan Magenheimer > Signed-off-by: Minchan Kim > --- > mm/page_io.c | 35 +++++++++++++++++++++++++++++++++++ > 1 file changed, 35 insertions(+) > > diff --git a/mm/page_io.c b/mm/page_io.c > index a294076..527db57 100644 > --- a/mm/page_io.c > +++ b/mm/page_io.c > @@ -21,6 +21,7 @@ > #include > #include > #include > +#include > #include > > static struct bio *get_swap_bio(gfp_t gfp_flags, > @@ -82,8 +83,42 @@ void end_swap_bio_read(struct bio *bio, int err, struct batch_complete *batch) > 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) { > + /* > + * Swap subsystem does lazy swap slot free with > + * expecting the page would be swapped out again > + * so we can avoid unnecessary write if the page > + * isn't redirty. > + * It's good for real swap storage because we can > + * reduce unnecessary I/O and enhance wear-leveling > + * if you use SSD as swap device. > + * But if you use in-memory swap device(ex, zram), > + * it causes duplicated copy between uncompressed > + * data in VM-owned memory and compressed data in > + * zram-owned memory. So let's free zram-owned memory > + * and make the VM-owned decompressed page *dirty* > + * so the page should be swap out somewhere again if > + * we want to reclaim it, again. > + */ > + struct gendisk *disk = sis->bdev->bd_disk; > + if (disk->fops->swap_slot_free_notify) { > + swp_entry_t entry; > + unsigned long offset; > + > + entry.val = page_private(page); > + offset = swp_offset(entry); > + > + SetPageDirty(page); > + disk->fops->swap_slot_free_notify(sis->bdev, > + offset); > + } > + } > } > + > unlock_page(page); > bio_put(bio); > } > -- > 1.8.2.1 > -- 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/