From 38c8e6180939e5619140b2e9e479cb26029ff8b1 Mon Sep 17 00:00:00 2001 From: Miquel van Smoorenburg Date: Tue, 6 Jan 2009 14:39:02 -0800 Subject: [PATCH] do_mpage_readpage(): don't submit lots of small bios on boundary While tracing I/O patterns with blktrace (a great tool) a few weeks ago I identified a minor issue in fs/mpage.c As the comment above mpage_readpages() says, a fs's get_block function will set BH_Boundary when it maps a block just before a block for which extra I/O is required. Since get_block() can map a range of pages, for all these pages the BH_Boundary flag will be set. But we only need to push what I/O we have accumulated at the last block of this range. This makes do_mpage_readpage() send out the largest possible bio instead of a bunch of page-sized ones in the BH_Boundary case. Signed-off-by: Miquel van Smoorenburg Cc: Nick Piggin Cc: Jens Axboe Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/mpage.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/fs/mpage.c b/fs/mpage.c index 552b80b3facc..46e977efd50a 100644 --- a/fs/mpage.c +++ b/fs/mpage.c @@ -308,7 +308,10 @@ alloc_new: goto alloc_new; } - if (buffer_boundary(map_bh) || (first_hole != blocks_per_page)) + relative_block = block_in_file - *first_logical_block; + nblocks = map_bh->b_size >> blkbits; + if ((buffer_boundary(map_bh) && relative_block == nblocks) || + (first_hole != blocks_per_page)) bio = mpage_bio_submit(READ, bio); else *last_block_in_bio = blocks[blocks_per_page - 1]; -- 2.20.1