For cheap seek, when we scan the region between si->lowset_bit
and scan_base, if san_base is greater than si->highest_bit, the
scan operation between si->highest_bit and scan_base is not
unnecessary.
This patch can be used to avoid scanning invalidated region for
cheap seek.
Signed-off-by: Chen Yucong <sla...@gmail.com>
---
mm/swapfile.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/mm/swapfile.c b/mm/swapfile.c
index beeeef8..7f0f27e 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -489,6 +489,7 @@ static unsigned long scan_swap_map(struct swap_info_struct
*si,
{
unsigned long offset;
unsigned long scan_base;
+ unsigned long upper_bound;
unsigned long last_in_cluster = 0;
int latency_ration = LATENCY_LIMIT;
@@ -551,9 +552,11 @@ static unsigned long scan_swap_map(struct swap_info_struct
*si,
offset = si->lowest_bit;
last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
+ upper_bound = (scan_base <= si->highest_bit) ?
+ scan_base : (si->highest_bit + 1);
/* Locate the first empty (unaligned) cluster */
- for (; last_in_cluster < scan_base; offset++) {
+ for (; last_in_cluster < upper_bound; offset++) {
if (si->swap_map[offset])
last_in_cluster = offset + SWAPFILE_CLUSTER;
else if (offset == last_in_cluster) {
--
1.7.10.4
--
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