Messages in this thread Patch in this message | | | From | Minchan Kim <> | Subject | [PATCH] mm: remove compressed copy from zram in-memory | Date | Mon, 8 Apr 2013 15:01:02 +0900 |
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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
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: Dan Magenheimer <dan.magenheimer@oracle.com> Signed-off-by: Minchan Kim <minchan@kernel.org> --- Fragment ratio is almost same but memory consumption and compile time is better. I am working to add defragment function of zsmalloc.
mm/page_io.c | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+)
diff --git a/mm/page_io.c b/mm/page_io.c index 78eee32..644900a 100644 --- a/mm/page_io.c +++ b/mm/page_io.c @@ -20,6 +20,7 @@ #include <linux/buffer_head.h> #include <linux/writeback.h> #include <linux/frontswap.h> +#include <linux/blkdev.h> #include <asm/pgtable.h> static struct bio *get_swap_bio(gfp_t gfp_flags, @@ -81,8 +82,30 @@ void end_swap_bio_read(struct bio *bio, int err) iminor(bio->bi_bdev->bd_inode), (unsigned long long)bio->bi_sector); } else { + /* + * There is no reason to keep both uncompressed data and + * compressed data in memory. + */ + 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) { + 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
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