From 1d1aff8cf367d2216a678c722161784e207965c4 Mon Sep 17 00:00:00 2001 From: Joseph Qi Date: Thu, 5 Nov 2015 18:43:58 -0800 Subject: [PATCH] ocfs2: improve performance for localalloc Currently cluster allocation is always trying to find a victim chain (a chian has most space), and this may lead to poor performance because of discontiguous allocation in some scenarios. Our test case is block size 4k, cluster size 1M and mount option with localalloc=2048 (2G), since a gd is 32256M (about 31.5G) and a localalloc window is only 2G, creating 50G file will result in 2G from gd0, 2G from gd1, ... One way to improve performance is enlarge localalloc window size (max 31104M), but this will make end user feel that about 30G is suddenly "missing", and localalloc currently do not support steal, which means one node cannot use another node's localalloc even it is not used in fact. So using the last gd to record the allocation and continues with the gd if it has enough space for a localalloc window can make the allocation as more contiguous as possible. Our test result is below (evaluated in IOPS), which is using iometer running in VM, dynamic vhd virtual disk stored in ocfs2. IO model Original After Improved(%) 16K60%Write100%Random 703 876 24.59% 8K90%Write100%Random 735 827 12.59% 4K100%Write100%Random 859 915 6.52% 4K100%Read100%Random 2092 2600 24.30% Signed-off-by: Joseph Qi Tested-by: Norton Zhu Cc: Mark Fasheh Cc: Joel Becker Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/ocfs2/suballoc.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/fs/ocfs2/suballoc.c b/fs/ocfs2/suballoc.c index d83d260..fc6d25f 100644 --- a/fs/ocfs2/suballoc.c +++ b/fs/ocfs2/suballoc.c @@ -1920,7 +1920,10 @@ static int ocfs2_claim_suballoc_bits(struct ocfs2_alloc_context *ac, status = ocfs2_search_chain(ac, handle, bits_wanted, min_bits, res, &bits_left); if (!status) { - hint = ocfs2_group_from_res(res); + if (ocfs2_is_cluster_bitmap(ac->ac_inode)) + hint = res->sr_bg_blkno; + else + hint = ocfs2_group_from_res(res); goto set_hint; } if (status < 0 && status != -ENOSPC) { -- 2.7.4