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authorRik van Riel <riel@redhat.com>2012-03-21 16:33:50 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-03-21 17:54:56 -0700
commit67f96aa252e606cdf6c3cf1032952ec207ec0cf0 (patch)
treea5a4299dd32789831eda558b51c0120272846664 /mm/swapfile.c
parentc38446cc65e1f2b3eb8630c53943b94c4f65f670 (diff)
downloadlinux-67f96aa252e606cdf6c3cf1032952ec207ec0cf0.tar.gz
mm: make swapin readahead skip over holes
Ever since abandoning the virtual scan of processes, for scalability reasons, swap space has been a little more fragmented than before. This can lead to the situation where a large memory user is killed, swap space ends up full of "holes" and swapin readahead is totally ineffective. On my home system, after killing a leaky firefox it took over an hour to page just under 2GB of memory back in, slowing the virtual machines down to a crawl. This patch makes swapin readahead simply skip over holes, instead of stopping at them. This allows the system to swap things back in at rates of several MB/second, instead of a few hundred kB/second. The checks done in valid_swaphandles are already done in read_swap_cache_async as well, allowing us to remove a fair amount of code. [akpm@linux-foundation.org: fix it for page_cluster >= 32] Signed-off-by: Rik van Riel <riel@redhat.com> Cc: Minchan Kim <minchan.kim@gmail.com> Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Mel Gorman <mgorman@suse.de> Cc: Adrian Drzewiecki <z@drze.net> Cc: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/swapfile.c')
-rw-r--r--mm/swapfile.c52
1 files changed, 0 insertions, 52 deletions
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 44595a373e4..b82c028cfcc 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -2288,58 +2288,6 @@ int swapcache_prepare(swp_entry_t entry)
}
/*
- * swap_lock prevents swap_map being freed. Don't grab an extra
- * reference on the swaphandle, it doesn't matter if it becomes unused.
- */
-int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
-{
- struct swap_info_struct *si;
- int our_page_cluster = page_cluster;
- pgoff_t target, toff;
- pgoff_t base, end;
- int nr_pages = 0;
-
- if (!our_page_cluster) /* no readahead */
- return 0;
-
- si = swap_info[swp_type(entry)];
- target = swp_offset(entry);
- base = (target >> our_page_cluster) << our_page_cluster;
- end = base + (1 << our_page_cluster);
- if (!base) /* first page is swap header */
- base++;
-
- spin_lock(&swap_lock);
- if (end > si->max) /* don't go beyond end of map */
- end = si->max;
-
- /* Count contiguous allocated slots above our target */
- for (toff = target; ++toff < end; nr_pages++) {
- /* Don't read in free or bad pages */
- if (!si->swap_map[toff])
- break;
- if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD)
- break;
- }
- /* Count contiguous allocated slots below our target */
- for (toff = target; --toff >= base; nr_pages++) {
- /* Don't read in free or bad pages */
- if (!si->swap_map[toff])
- break;
- if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD)
- break;
- }
- spin_unlock(&swap_lock);
-
- /*
- * Indicate starting offset, and return number of pages to get:
- * if only 1, say 0, since there's then no readahead to be done.
- */
- *offset = ++toff;
- return nr_pages? ++nr_pages: 0;
-}
-
-/*
* add_swap_count_continuation - called when a swap count is duplicated
* beyond SWAP_MAP_MAX, it allocates a new page and links that to the entry's
* page of the original vmalloc'ed swap_map, to hold the continuation count