From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from acsinet15.oracle.com ([141.146.126.227]:27234 "EHLO acsinet15.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755091Ab2H1AWK (ORCPT ); Mon, 27 Aug 2012 20:22:10 -0400 Message-ID: <503C0F2A.9040308@oracle.com> Date: Tue, 28 Aug 2012 08:22:02 +0800 From: Liu Bo MIME-Version: 1.0 To: Josef Bacik CC: "linux-btrfs@vger.kernel.org" Subject: Re: [PATCH 2/2] Btrfs: improve fsync by filtering extents that we want References: <1346086340-14776-1-git-send-email-bo.li.liu@oracle.com> <1346086340-14776-2-git-send-email-bo.li.liu@oracle.com> <20120827171240.GC4048@localhost.localdomain> In-Reply-To: <20120827171240.GC4048@localhost.localdomain> Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-btrfs-owner@vger.kernel.org List-ID: 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 >> --- >> 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. thanks, liubo