From patchwork Thu Sep 5 08:47:10 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Dave Chinner X-Patchwork-Id: 11132473 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 0125213B1 for ; Thu, 5 Sep 2019 08:47:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E055421848 for ; Thu, 5 Sep 2019 08:47:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732041AbfIEIr1 (ORCPT ); Thu, 5 Sep 2019 04:47:27 -0400 Received: from mail104.syd.optusnet.com.au ([211.29.132.246]:44157 "EHLO mail104.syd.optusnet.com.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732488AbfIEIr0 (ORCPT ); Thu, 5 Sep 2019 04:47:26 -0400 Received: from dread.disaster.area (pa49-181-255-194.pa.nsw.optusnet.com.au [49.181.255.194]) by mail104.syd.optusnet.com.au (Postfix) with ESMTPS id 8BBBC43DE8E for ; Thu, 5 Sep 2019 18:47:20 +1000 (AEST) Received: from discord.disaster.area ([192.168.253.110]) by dread.disaster.area with esmtp (Exim 4.92) (envelope-from ) id 1i5nQE-0004Cc-Qr for linux-xfs@vger.kernel.org; Thu, 05 Sep 2019 18:47:18 +1000 Received: from dave by discord.disaster.area with local (Exim 4.92) (envelope-from ) id 1i5nQE-0007xn-Oq for linux-xfs@vger.kernel.org; Thu, 05 Sep 2019 18:47:18 +1000 From: Dave Chinner To: linux-xfs@vger.kernel.org Subject: [PATCH 1/8] xfs: push the AIL in xlog_grant_head_wake Date: Thu, 5 Sep 2019 18:47:10 +1000 Message-Id: <20190905084717.30308-2-david@fromorbit.com> X-Mailer: git-send-email 2.23.0.rc1 In-Reply-To: <20190905084717.30308-1-david@fromorbit.com> References: <20190905084717.30308-1-david@fromorbit.com> MIME-Version: 1.0 X-Optus-CM-Score: 0 X-Optus-CM-Analysis: v=2.2 cv=D+Q3ErZj c=1 sm=1 tr=0 a=YO9NNpcXwc8z/SaoS+iAiA==:117 a=YO9NNpcXwc8z/SaoS+iAiA==:17 a=jpOVt7BSZ2e4Z31A5e1TngXxSK0=:19 a=J70Eh1EUuV4A:10 a=20KFwNOVAAAA:8 a=GXCpdPv9Ty4ubGbr0XkA:9 Sender: linux-xfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org From: Dave Chinner In the situation where the log is full and the CIL has not recently flushed, the AIL push threshold is throttled back to the where the last write of the head of the log was completed. This is stored in log->l_last_sync_lsn. Hence if the CIL holds > 25% of the log space pinned by flushes and/or aggregation in progress, we can get the situation where the head of the log lags a long way behind the reservation grant head. When this happens, the AIL push target is trimmed back from where the reservation grant head wants to push the log tail to, back to where the head of the log currently is. This means the push target doesn't reach far enough into the log to actually move the tail before the transaction reservation goes to sleep. When the CIL push completes, it moves the log head forward such that the AIL push target can now be moved, but that has no mechanism for puhsing the log tail. Further, if the next tail movement of the log is not large enough wake the waiter (i.e. still not enough space for it to have a reservation granted), we don't wake anything up, and hence we do not update the AIL push target to take into account the head of the log moving and allowing the push target to be moved forwards. To avoid this particular condition, if we fail to wake the first waiter on the grant head because we don't have enough space, push on the AIL again. This will pick up any movement of the log head and allow the push target to move forward due to completion of CIL pushing. Signed-off-by: Dave Chinner --- fs/xfs/xfs_log.c | 23 ++++++++++++++++++++++- 1 file changed, 22 insertions(+), 1 deletion(-) diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c index b159a9e9fef0..5e21450fb8f5 100644 --- a/fs/xfs/xfs_log.c +++ b/fs/xfs/xfs_log.c @@ -214,15 +214,36 @@ xlog_grant_head_wake( { struct xlog_ticket *tic; int need_bytes; + bool woken_task = false; list_for_each_entry(tic, &head->waiters, t_queue) { + /* + * The is a chance that the size of the CIL checkpoints in + * progress result at the last AIL push resulted in the log head + * (l_last_sync_lsn) not reflecting where the log head now is. + * Hence when we are woken here, it may be the head of the log + * that has moved rather than the tail. In that case, the tail + * didn't move and there won't be space available until the AIL + * push target is updated and the tail pushed again. If the AIL + * is already pushed to it's target, we will hang here until + * something else updates the AIL push target. + * + * Hence if there isn't space to wake the first waiter on the + * grant head, we need to push the AIL again to ensure the + * target reflects the current log tail and log head position + * before we wait for the tail to move again. + */ need_bytes = xlog_ticket_reservation(log, head, tic); - if (*free_bytes < need_bytes) + if (*free_bytes < need_bytes) { + if (!woken_task) + xlog_grant_push_ail(log, need_bytes); return false; + } *free_bytes -= need_bytes; trace_xfs_log_grant_wake_up(log, tic); wake_up_process(tic->t_task); + woken_task = true; } return true;