From: Andi Kleen The original INT_MAX is too large, reduce it to - avoid unnecessarily dirtying/bouncing the cache line - restore mmap read-around faster on changed access pattern Background: in the mosbench exim benchmark which does multi-threaded page faults on shared struct file, the ra->mmap_miss updates are found to cause excessive cache line bouncing on tmpfs. The ra state updates are needless for tmpfs because it actually disabled readahead totally (shmem_backing_dev_info.ra_pages == 0). Tested-by: Tim Chen Signed-off-by: Andi Kleen Signed-off-by: Wu Fengguang --- mm/filemap.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- linux-next.orig/mm/filemap.c 2011-04-23 09:01:44.000000000 +0800 +++ linux-next/mm/filemap.c 2011-04-23 09:17:21.000000000 +0800 @@ -1538,7 +1538,8 @@ static void do_sync_mmap_readahead(struc return; } - if (ra->mmap_miss < INT_MAX) + /* Avoid banging the cache line if not needed */ + if (ra->mmap_miss < MMAP_LOTSAMISS * 10) ra->mmap_miss++; /* -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/