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swap: make each swap partition have one address_space

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When I use several fast SSD to do swap, swapper_space.tree_lock is
heavily contended.  This makes each swap partition have one
address_space to reduce the lock contention.  There is an array of
address_space for swap.  The swap entry type is the index to the array.

In my test with 3 SSD, this increases the swapout throughput 20%.

[akpm@linux-foundation.org: revert unneeded change to  __add_to_swap_cache]
Signed-off-by: Shaohua Li <shli@fusionio.com>
Cc: Hugh Dickins <hughd@google.com>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Shaohua Li
2013-02-22 16:34:37 -08:00
committed by Linus Torvalds
parent 9800339b5e
commit 33806f06da
8 changed files with 67 additions and 34 deletions
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10
mm/util.c
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@ -6,6 +6,7 @@
#include <linux/sched.h>
#include <linux/security.h>
#include <linux/swap.h>
#include <linux/swapops.h>
#include <asm/uaccess.h>
#include "internal.h"
@ -389,9 +390,12 @@ struct address_space *page_mapping(struct page *page)
VM_BUG_ON(PageSlab(page));
#ifdef CONFIG_SWAP
if (unlikely(PageSwapCache(page)))
mapping = &swapper_space;
else
if (unlikely(PageSwapCache(page))) {
swp_entry_t entry;
entry.val = page_private(page);
mapping = swap_address_space(entry);
} else
#endif
if ((unsigned long)mapping & PAGE_MAPPING_ANON)
mapping = NULL;