The patch titled
Subject: mm: remove compressed copy from zram in-memory
has been added to the -mm tree. Its filename is
mm-remove-compressed-copy-from-zram-in-memory.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/SubmitChecklist when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Minchan Kim <minchan@xxxxxxxxxx>
Subject: mm: remove compressed copy from zram in-memory
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
* changelog from v3
* Rebased on next-20130508
* changelog from v1
* Add more comment
Signed-off-by: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>
Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Seth Jennings <sjenning@xxxxxxxxxxxxxxxxxx>
Cc: Nitin Gupta <ngupta@xxxxxxxxxx>
Cc: Konrad Rzeszutek Wilk <konrad@xxxxxxxxxx>
Cc: Shaohua Li <shli@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_io.c | 35 +++++++++++++++++++++++++++++++++++
1 file changed, 35 insertions(+)
diff -puN mm/page_io.c~mm-remove-compressed-copy-from-zram-in-memory mm/page_io.c
--- a/mm/page_io.c~mm-remove-compressed-copy-from-zram-in-memory
+++ a/mm/page_io.c
@@ -21,6 +21,7 @@
#include <linux/writeback.h>
#include <linux/frontswap.h>
#include <linux/aio.h>
+#include <linux/blkdev.h>
#include <asm/pgtable.h>
static struct bio *get_swap_bio(gfp_t gfp_flags,
@@ -81,8 +82,42 @@ void end_swap_bio_read(struct bio *bio,
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);
}
_
Patches currently in -mm which might be from minchan@xxxxxxxxxx are
origin.patch
mm-remove-compressed-copy-from-zram-in-memory.patch
mm-add-vm-event-counters-for-balloon-pages-compaction.patch
block-aio-batch-completion-for-bios-kiocbs.patch
debugging-keep-track-of-page-owners-fix-2.patch
debugging-keep-track-of-page-owners-fix-2-fix.patch
debugging-keep-track-of-page-owners-fix-2-fix-fix.patch
--
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
