From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.fusionio.com ([66.114.96.30]:59851 "EHLO mx1.fusionio.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753420Ab2H0RMm (ORCPT ); Mon, 27 Aug 2012 13:12:42 -0400 Date: Mon, 27 Aug 2012 13:12:40 -0400 From: Josef Bacik To: Liu Bo CC: "linux-btrfs@vger.kernel.org" , Josef Bacik Subject: Re: [PATCH 2/2] Btrfs: improve fsync by filtering extents that we want Message-ID: <20120827171240.GC4048@localhost.localdomain> References: <1346086340-14776-1-git-send-email-bo.li.liu@oracle.com> <1346086340-14776-2-git-send-email-bo.li.liu@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" In-Reply-To: <1346086340-14776-2-git-send-email-bo.li.liu@oracle.com> Sender: linux-btrfs-owner@vger.kernel.org List-ID: 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 > --- > 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; > 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? Thanks, Josef