From patchwork Tue May 10 19:57:27 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: y@vger.kernel.org X-Patchwork-Id: 775202 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by demeter1.kernel.org (8.14.4/8.14.3) with ESMTP id p4AJtErN014760 for ; Tue, 10 May 2011 19:55:14 GMT Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752207Ab1EJTzK (ORCPT ); Tue, 10 May 2011 15:55:10 -0400 Received: from smtp.gentoo.org ([140.211.166.183]:40711 "EHLO smtp.gentoo.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751536Ab1EJTzI (ORCPT ); Tue, 10 May 2011 15:55:08 -0400 Received: from gentoo.org (unknown [178.121.233.111]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) (Authenticated sender: slyfox) by smtp.gentoo.org (Postfix) with ESMTPSA id E581B1BC0E2; Tue, 10 May 2011 19:55:05 +0000 (UTC) Received: by gentoo.org (sSMTP sendmail emulation); Tue, 10 May 2011 22:57:49 +0300 From: y@vger.kernel.org To: linux-btrfs@vger.kernel.org Cc: Chris Mason , Sergei Trofimovich Subject: [PATCH v2 1/3] btrfs: don't spin in shrink_delalloc if there is nothing to free Date: Tue, 10 May 2011 22:57:27 +0300 Message-Id: <1305057449-12075-2-git-send-email-y> X-Mailer: git-send-email 1.7.3.4 In-Reply-To: <1305057449-12075-1-git-send-email-y> References: <1305057449-12075-1-git-send-email-y> Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org X-Greylist: IP, sender and recipient auto-whitelisted, not delayed by milter-greylist-4.2.6 (demeter1.kernel.org [140.211.167.41]); Tue, 10 May 2011 19:55:14 +0000 (UTC) From: Sergei Trofimovich Observed as a large delay when --mixed filesystem is filled up. Test example: 1. create tiny --mixed FS: $ dd if=/dev/zero of=2G.img seek=$((2048 * 1024 * 1024 - 1)) count=1 bs=1 $ mkfs.btrfs --mixed 2G.img $ mount -oloop 2G.img /mnt/ut/ 2. Try to fill it up: $ dd if=/dev/urandom of=10M.file bs=10240 count=1024 $ seq 1 256 | while read file_no; do echo $file_no; time cp 10M.file ${file_no}.copy; done Up to '200.copy' it goes fast, but when disk fills-up each -ENOSPC message takes 3 seconds to pop-up _every_ ENOSPC (and in usermode linux it's even more: 30-60 seconds!). (Maybe, time depends on kernel's timer resolution). No IO, no CPU load, just rescheduling. Some debugging revealed busy spinning in shrink_delalloc. Signed-off-by: Sergei Trofimovich Reviewed-by: Josef Bacik --- fs/btrfs/extent-tree.c | 4 ++++ 1 files changed, 4 insertions(+), 0 deletions(-) diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index 9ee6bd5..9f5fdd3 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -3425,6 +3425,10 @@ static int shrink_delalloc(struct btrfs_trans_handle *trans, if (reserved == 0) return 0; + /* nothing to shrink - nothing to reclaim */ + if (root->fs_info->delalloc_bytes == 0) + return 0; + max_reclaim = min(reserved, to_reclaim); while (loops < 1024) {