From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-we0-f178.google.com ([74.125.82.178]:36702 "EHLO mail-we0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754477Ab3KVSzG (ORCPT ); Fri, 22 Nov 2013 13:55:06 -0500 Received: by mail-we0-f178.google.com with SMTP id u56so1525595wes.37 for ; Fri, 22 Nov 2013 10:55:05 -0800 (PST) From: Filipe David Borba Manana To: linux-btrfs@vger.kernel.org Cc: Filipe David Borba Manana Subject: [PATCH v2] Btrfs: avoid unnecessary ordered extent cache resets Date: Fri, 22 Nov 2013 18:54:58 +0000 Message-Id: <1385146498-6549-1-git-send-email-fdmanana@gmail.com> In-Reply-To: <1385139163-7539-1-git-send-email-fdmanana@gmail.com> References: <1385139163-7539-1-git-send-email-fdmanana@gmail.com> Sender: linux-btrfs-owner@vger.kernel.org List-ID: After an ordered extent completes, don't blindly reset the inode's ordered tree last accessed ordered extent pointer. While running the xfstests I noticed that about 29% of the time the ordered extent to which tree->last pointed was not the same as our just completed ordered extent. After that I ran the following sysbench test (after a prepare phase) and noticed that about 68% of the time tree->last pointed to a different ordered extent too. sysbench --test=fileio --file-num=32 --file-total-size=4G \ --file-test-mode=rndwr --num-threads=512 \ --file-block-size=32768 --max-time=60 --max-requests=0 run Therefore reset tree->last on ordered extent removal only if it pointed to the ordered extent we're removing from the tree. Results from 4 runs of the following test before and after applying this patch: $ sysbench --test=fileio --file-num=32 --file-total-size=4G \ --file-test-mode=seqwr --num-threads=512 \ --file-block-size=32768 --max-time=60 --file-io-mode=sync prepare $ sysbench --test=fileio --file-num=32 --file-total-size=4G \ --file-test-mode=seqwr --num-threads=512 \ --file-block-size=32768 --max-time=60 --file-io-mode=sync run Before this path: run 1 - 64.049Mb/sec run 2 - 63.455Mb/sec run 3 - 64.656Mb/sec run 4 - 63.833Mb/sec After this patch: run 1 - 66.149Mb/sec run 2 - 68.459Mb/sec run 3 - 66.338Mb/sec run 4 - 66.176Mb/sec With random writes (--file-test-mode=rndwr) I had huge fluctuations on the results (+- 35% easily). Signed-off-by: Filipe David Borba Manana --- V2: Updated commit message with benchmark results. fs/btrfs/ordered-data.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/btrfs/ordered-data.c b/fs/btrfs/ordered-data.c index 69582d5..b8c2ded 100644 --- a/fs/btrfs/ordered-data.c +++ b/fs/btrfs/ordered-data.c @@ -520,7 +520,8 @@ void btrfs_remove_ordered_extent(struct inode *inode, spin_lock_irq(&tree->lock); node = &entry->rb_node; rb_erase(node, &tree->tree); - tree->last = NULL; + if (tree->last == node) + tree->last = NULL; set_bit(BTRFS_ORDERED_COMPLETE, &entry->flags); spin_unlock_irq(&tree->lock); -- 1.7.9.5