On Mon, Aug 27, 2012 at 06:22:02PM -0600, Liu Bo wrote: > On 08/28/2012 01:12 AM, Josef Bacik wrote: > > On Mon, Aug 27, 2012 at 10:52:20AM -0600, Liu Bo wrote: > >> This is based on Josef's "Btrfs: turbo charge fsync". > >> > >> The above Josef's patch performs very good in random sync write test, > >> because we won't have too much extents to merge. > >> > >> However, it does not performs good on the test: > >> dd if=/dev/zero of=foobar bs=4k count=12500 oflag=sync > >> > >> The reason is when we do sequencial sync write, we need to merge the > >> current extent just with the previous one, so that we can get accumulated > >> extents to log: > >> > >> A(4k) --> AA(8k) --> AAA(12k) --> AAAA(16k) ... > >> > >> So we'll have to flush more and more checksum into log tree, which is the > >> bottleneck according to my tests. > >> > >> But we can avoid this by telling fsync the real extents that are needed > >> to be logged. > >> > >> With this, I did the above dd sync write test (size=50m), > >> > >> w/o (orig) w/ (josef's) w/ (this) > >> SATA 104KB/s 109KB/s 121KB/s > >> ramdisk 1.5MB/s 1.5MB/s 10.7MB/s (613%) > >> > >> Signed-off-by: Liu Bo <[email protected]> > >> --- > >> fs/btrfs/extent_map.c | 20 ++++++++++++++++++++ > >> fs/btrfs/extent_map.h | 2 ++ > >> fs/btrfs/inode.c | 1 + > >> fs/btrfs/tree-log.c | 6 +++--- > >> 4 files changed, 26 insertions(+), 3 deletions(-) > >> > >> diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c > >> index 1fe82cf..ac606f0 100644 > >> --- a/fs/btrfs/extent_map.c > >> +++ b/fs/btrfs/extent_map.c > >> @@ -203,6 +203,8 @@ static void try_merge_map(struct extent_map_tree > >> *tree, struct extent_map *em) > >> em->block_start = merge->block_start; > >> merge->in_tree = 0; > >> if (merge->generation > em->generation) { > >> + em->mod_start = em->start; > >> + em->mod_len = em->len; > > > > Shouldn't this be > > > > em->mod_start = merge->start; > > em->mod_len += merge_len; > > > > They just do the same thing. > > There is already a > em->start = merge->start; > em->len += merge_len > > >> em->generation = merge->generation; > >> list_move(&em->list, &tree->modified_extents); > >> } > >> @@ -222,6 +224,7 @@ static void try_merge_map(struct extent_map_tree > >> *tree, struct extent_map *em) > >> rb_erase(&merge->rb_node, &tree->map); > >> merge->in_tree = 0; > >> if (merge->generation > em->generation) { > >> + em->mod_len = em->len; > > > > And this should be em->mod_len += em->len? > > > > No, em->len has already contained the merge's len. >
Duh right sorry. Thanks, Josef -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
