The patch titled
Subject: mm: make swapin readahead skip over holes
has been added to the -mm tree. Its filename is
make-swapin-readahead-skip-over-holes.patch
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From: Rik van Riel <riel@xxxxxxxxxx>
Subject: 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.
Signed-off-by: Rik van Riel <riel@xxxxxxxxxx>
Cc: Minchan Kim <minchan.kim@xxxxxxxxx>
Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Acked-by: Mel Gorman <mgorman@xxxxxxx>
Cc: Adrian Drzewieki <z@xxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/swap.h | 1
mm/swap_state.c | 24 ++++++++----------
mm/swapfile.c | 52 -----------------------------------------
3 files changed, 11 insertions(+), 66 deletions(-)
diff -puN include/linux/swap.h~make-swapin-readahead-skip-over-holes include/linux/swap.h
--- a/include/linux/swap.h~make-swapin-readahead-skip-over-holes
+++ a/include/linux/swap.h
@@ -329,7 +329,6 @@ extern long total_swap_pages;
extern void si_swapinfo(struct sysinfo *);
extern swp_entry_t get_swap_page(void);
extern swp_entry_t get_swap_page_of_type(int);
-extern int valid_swaphandles(swp_entry_t, unsigned long *);
extern int add_swap_count_continuation(swp_entry_t, gfp_t);
extern void swap_shmem_alloc(swp_entry_t);
extern int swap_duplicate(swp_entry_t);
diff -puN mm/swap_state.c~make-swapin-readahead-skip-over-holes mm/swap_state.c
--- a/mm/swap_state.c~make-swapin-readahead-skip-over-holes
+++ a/mm/swap_state.c
@@ -382,25 +382,23 @@ struct page *read_swap_cache_async(swp_e
struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask,
struct vm_area_struct *vma, unsigned long addr)
{
- int nr_pages;
struct page *page;
- unsigned long offset;
- unsigned long end_offset;
+ unsigned long offset = swp_offset(entry);
+ unsigned long start_offset, end_offset;
+ unsigned long mask = (1 << page_cluster) - 1;
- /*
- * Get starting offset for readaround, and number of pages to read.
- * Adjust starting address by readbehind (for NUMA interleave case)?
- * No, it's very unlikely that swap layout would follow vma layout,
- * more likely that neighbouring swap pages came from the same node:
- * so use the same "addr" to choose the same node for each swap read.
- */
- nr_pages = valid_swaphandles(entry, &offset);
- for (end_offset = offset + nr_pages; offset < end_offset; offset++) {
+ /* Read a page_cluster sized and aligned cluster around offset. */
+ start_offset = offset & ~mask;
+ end_offset = offset | mask;
+ if (!start_offset) /* First page is swap header. */
+ start_offset++;
+
+ for (offset = start_offset; offset <= end_offset ; offset++) {
/* Ok, do the async read-ahead now */
page = read_swap_cache_async(swp_entry(swp_type(entry), offset),
gfp_mask, vma, addr);
if (!page)
- break;
+ continue;
page_cache_release(page);
}
lru_add_drain(); /* Push any new pages onto the LRU now */
diff -puN mm/swapfile.c~make-swapin-readahead-skip-over-holes mm/swapfile.c
--- a/mm/swapfile.c~make-swapin-readahead-skip-over-holes
+++ a/mm/swapfile.c
@@ -2290,58 +2290,6 @@ 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
_
Subject: Subject: mm: make swapin readahead skip over holes
Patches currently in -mm which might be from riel@xxxxxxxxxx are
origin.patch
linux-next.patch
mm-vmscanc-cleanup-with-s-reclaim_mode-isolate_mode.patch
mm-vmscan-fix-misused-nr_reclaimed-in-shrink_mem_cgroup_zone.patch
make-swapin-readahead-skip-over-holes.patch
make-swapin-readahead-skip-over-holes-fix.patch
mm-fix-page-faults-detection-in-swap-token-logic.patch
mm-add-extra-free-kbytes-tunable.patch
mm-add-extra-free-kbytes-tunable-update.patch
mm-add-extra-free-kbytes-tunable-update-checkpatch-fixes.patch
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