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authorMinchan Kim2013-07-03 17:01:24 -0500
committerRom Lemarchand2013-09-26 19:05:10 -0500
commit4fe1f96d0bc0cce09c41a6818153fea81d645a39 (patch)
tree07ac88b7739607f0cd55ba552e9b0e27386b2ede
parent79245d37165aad2e57b1919defdd124639ddf55a (diff)
downloadkernel-common-android-3.10.tar.gz
kernel-common-android-3.10.tar.xz
kernel-common-android-3.10.zip
mm: remove compressed copy from zram in-memoryandroid-3.10
Swap subsystem does lazy swap slot free with expecting the page would be swapped out again so we can avoid unnecessary write. But the problem in in-memory swap(ex, zram) is that it consumes 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, 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 be written out the swap device to reclaim it. It means we never lose it. I tested this patch with kernel compile workload. 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 [akpm@linux-foundation.org: tweak comment text] [artem.savkov@gmail.com: fix BUG due to non-swapcache pages in end_swap_bio_read()] [akpm@linux-foundation.org: invert unlikely() test, augment comment, 80-col cleanup] Signed-off-by: Dan Magenheimer <dan.magenheimer@oracle.com> Signed-off-by: Minchan Kim <minchan@kernel.org> Signed-off-by: Artem Savkov <artem.savkov@gmail.com> Cc: Hugh Dickins <hughd@google.com> Cc: Seth Jennings <sjenning@linux.vnet.ibm.com> Cc: Nitin Gupta <ngupta@vflare.org> Cc: Konrad Rzeszutek Wilk <konrad@darnok.org> Cc: Shaohua Li <shli@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/page_io.c50
1 files changed, 48 insertions, 2 deletions
diff --git a/mm/page_io.c b/mm/page_io.c
index a8a3ef45fed..ba05b64e5d8 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -21,6 +21,7 @@
21#include <linux/writeback.h> 21#include <linux/writeback.h>
22#include <linux/frontswap.h> 22#include <linux/frontswap.h>
23#include <linux/aio.h> 23#include <linux/aio.h>
24#include <linux/blkdev.h>
24#include <asm/pgtable.h> 25#include <asm/pgtable.h>
25 26
26static struct bio *get_swap_bio(gfp_t gfp_flags, 27static struct bio *get_swap_bio(gfp_t gfp_flags,
@@ -80,9 +81,54 @@ void end_swap_bio_read(struct bio *bio, int err)
80 imajor(bio->bi_bdev->bd_inode), 81 imajor(bio->bi_bdev->bd_inode),
81 iminor(bio->bi_bdev->bd_inode), 82 iminor(bio->bi_bdev->bd_inode),
82 (unsigned long long)bio->bi_sector); 83 (unsigned long long)bio->bi_sector);
83 } else { 84 goto out;
84 SetPageUptodate(page);
85 } 85 }
86
87 SetPageUptodate(page);
88
89 /*
90 * There is no guarantee that the page is in swap cache - the software
91 * suspend code (at least) uses end_swap_bio_read() against a non-
92 * swapcache page. So we must check PG_swapcache before proceeding with
93 * this optimization.
94 */
95 if (likely(PageSwapCache(page))) {
96 struct swap_info_struct *sis;
97
98 sis = page_swap_info(page);
99 if (sis->flags & SWP_BLKDEV) {
100 /*
101 * The swap subsystem performs lazy swap slot freeing,
102 * expecting that the page will be swapped out again.
103 * So we can avoid an unnecessary write if the page
104 * isn't redirtied.
105 * This is good for real swap storage because we can
106 * reduce unnecessary I/O and enhance wear-leveling
107 * if an SSD is used as the as swap device.
108 * But if in-memory swap device (eg zram) is used,
109 * this causes a duplicated copy between uncompressed
110 * data in VM-owned memory and compressed data in
111 * zram-owned memory. So let's free zram-owned memory
112 * and make the VM-owned decompressed page *dirty*,
113 * so the page should be swapped out somewhere again if
114 * we again wish to reclaim it.
115 */
116 struct gendisk *disk = sis->bdev->bd_disk;
117 if (disk->fops->swap_slot_free_notify) {
118 swp_entry_t entry;
119 unsigned long offset;
120
121 entry.val = page_private(page);
122 offset = swp_offset(entry);
123
124 SetPageDirty(page);
125 disk->fops->swap_slot_free_notify(sis->bdev,
126 offset);
127 }
128 }
129 }
130
131out:
86 unlock_page(page); 132 unlock_page(page);
87 bio_put(bio); 133 bio_put(bio);
88} 134}