Commit af21ca8e authored May 14, 2013 by Bob Peterson Committed by Steven Whitehouse May 24, 2013

GFS2: Use single-block reservations for directories



This patch changes the multi-block allocation code, such that
directory inodes only get a single block reserved in the bitmap.
That way, the bitmaps are more tightly packed together, and there
are fewer spans of free blocks for in-use block reservations.
This means it takes less time to find a free span of blocks in the
bitmap, which speeds things up. This increases the performance of
some workloads by almost 2X. In Nate's mockup.py script (which does
(1) create dir, (2) create dir in dir, (3) create file in that dir)
the test executes in 23 steps rather than 43 steps, a 47%
performance improvement.

Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

parent 37f71577

fs/gfs2/rgrp.c

+7 −2

Original line number	Diff line number	Diff line
		@@ -1401,9 +1401,14 @@ static void rg_mblk_search(struct gfs2_rgrpd rgd, struct gfs2_inode ip,
		u32 extlen;
		u32 free_blocks = rgd->rd_free_clone - rgd->rd_reserved;
		int ret;
		struct inode *inode = &ip->i_inode;

		if (S_ISDIR(inode->i_mode))
		extlen = 1;
		else {
		extlen = max_t(u32, atomic_read(&rs->rs_sizehint), requested);
		extlen = clamp(extlen, RGRP_RSRV_MINBLKS, free_blocks);
		}
		if ((rgd->rd_free_clone < rgd->rd_reserved) \|\| (free_blocks < extlen))
		return;

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