From: Huang Ying <[email protected]> In this patch, the size of the swap cluster is changed to that of the THP (Transparent Huge Page) on x86_64 architecture (512). This is for the THP swap support on x86_64. Where one swap cluster will be used to hold the contents of each THP swapped out. And some information of the swapped out THP (such as compound map count) will be recorded in the swap_cluster_info data structure.
In effect, this will enlarge swap cluster size by 2 times. Which may make it harder to find a free cluster when the swap space becomes fragmented. So that, this may reduce the continuous swap space allocation and sequential write in theory. The performance test in 0day show no regressions caused by this. Cc: Hugh Dickins <[email protected]> Cc: Shaohua Li <[email protected]> Cc: Minchan Kim <[email protected]> Cc: Rik van Riel <[email protected]> Signed-off-by: "Huang, Ying" <[email protected]> --- mm/swapfile.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/swapfile.c b/mm/swapfile.c index 8f1b97d..582912b 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -196,7 +196,7 @@ static void discard_swap_cluster(struct swap_info_struct *si, } } -#define SWAPFILE_CLUSTER 256 +#define SWAPFILE_CLUSTER 512 #define LATENCY_LIMIT 256 static inline void cluster_set_flag(struct swap_cluster_info *info, -- 2.8.1
