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author | Minchan Kim <minchan@kernel.org> | 2013-09-25 18:57:43 -0500 |
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committer | Simon Shields <keepcalm444@gmail.com> | 2016-06-12 21:20:21 +1000 |
commit | c72e09b31537cd8c558f70fd00d40c755e670114 (patch) | |
tree | 1f9782df9be80b6f0769aa89aa3b16a93c83fdb4 /mm | |
parent | 128faec612bd65b7c7b5318c47d35f4cabbc3060 (diff) | |
download | kernel_samsung_smdk4412-c72e09b31537cd8c558f70fd00d40c755e670114.zip kernel_samsung_smdk4412-c72e09b31537cd8c558f70fd00d40c755e670114.tar.gz kernel_samsung_smdk4412-c72e09b31537cd8c558f70fd00d40c755e670114.tar.bz2 |
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
[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>
Change-Id: I8f11fb7f0391954435002e7f290352f311c907d4
Signed-off-by: Paul Reioux <reioux@gmail.com>
Conflicts:
mm/page_io.c
Diffstat (limited to 'mm')
-rw-r--r-- | mm/page_io.c | 46 |
1 files changed, 44 insertions, 2 deletions
diff --git a/mm/page_io.c b/mm/page_io.c index dc76b4d..f57da45 100644 --- a/mm/page_io.c +++ b/mm/page_io.c @@ -18,6 +18,8 @@ #include <linux/bio.h> #include <linux/swapops.h> #include <linux/writeback.h> +#include <linux/aio.h> +#include <linux/blkdev.h> #include <asm/pgtable.h> static struct bio *get_swap_bio(gfp_t gfp_flags, @@ -78,9 +80,49 @@ void end_swap_bio_read(struct bio *bio, int err) imajor(bio->bi_bdev->bd_inode), iminor(bio->bi_bdev->bd_inode), (unsigned long long)bio->bi_sector); - } else { - SetPageUptodate(page); + goto out; + } + + SetPageUptodate(page); + + /* + * There is no guarantee that the page is in swap cache - the software + * suspend code (at least) uses end_swap_bio_read() against a non- + * swapcache page. So we must check PG_swapcache before proceeding with + * this optimization. + */ + if (likely(PageSwapCache(page))) { + /* + * The swap subsystem performs lazy swap slot freeing, + * expecting that the page will be swapped out again. + * So we can avoid an unnecessary write if the page + * isn't redirtied. + * This is good for real swap storage because we can + * reduce unnecessary I/O and enhance wear-leveling + * if an SSD is used as the as swap device. + * But if in-memory swap device (eg zram) is used, + * this causes a 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 swapped out somewhere again if + * we again wish to reclaim it. + */ + struct gendisk *disk = bio->bi_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(bio->bi_bdev, + offset); + } } + +out: unlock_page(page); bio_put(bio); } |