diff options
| author | Wu Fengguang <fengguang.wu@intel.com> | 2011-05-24 17:12:28 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2011-05-25 08:39:26 -0700 |
| commit | 275b12bf5486f6f531111fd3d7dbbf01df427cfe (patch) | |
| tree | ebed0109eaa3e4a015bc1653f4d933f2e84c794f | |
| parent | 1495f230fa7750479c79e3656286b9183d662077 (diff) | |
readahead: return early when readahead is disabled
Reduce readahead overheads by returning early in do_sync_mmap_readahead().
tmpfs has ra_pages=0 and it can page fault really fast (not constraint by
IO if not swapping).
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Tested-by: Tim Chen <tim.c.chen@intel.com>
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | mm/filemap.c | 12 |
1 files changed, 6 insertions, 6 deletions
diff --git a/mm/filemap.c b/mm/filemap.c index 88354ae0b1fd..c974a2863897 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -1556,6 +1556,8 @@ static void do_sync_mmap_readahead(struct vm_area_struct *vma, /* If we don't want any read-ahead, don't bother */ if (VM_RandomReadHint(vma)) return; + if (!ra->ra_pages) + return; if (VM_SequentialReadHint(vma) || offset - 1 == (ra->prev_pos >> PAGE_CACHE_SHIFT)) { @@ -1578,12 +1580,10 @@ static void do_sync_mmap_readahead(struct vm_area_struct *vma, * mmap read-around */ ra_pages = max_sane_readahead(ra->ra_pages); - if (ra_pages) { - ra->start = max_t(long, 0, offset - ra_pages/2); - ra->size = ra_pages; - ra->async_size = 0; - ra_submit(ra, mapping, file); - } + ra->start = max_t(long, 0, offset - ra_pages / 2); + ra->size = ra_pages; + ra->async_size = 0; + ra_submit(ra, mapping, file); } /* |