From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E9B8EC00306 for ; Fri, 6 Sep 2019 00:05:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1B765206BB for ; Fri, 6 Sep 2019 00:06:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730718AbfIFAF7 (ORCPT ); Thu, 5 Sep 2019 20:05:59 -0400 Received: from mail105.syd.optusnet.com.au ([211.29.132.249]:54381 "EHLO mail105.syd.optusnet.com.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388922AbfIFAF7 (ORCPT ); Thu, 5 Sep 2019 20:05:59 -0400 Received: from dread.disaster.area (pa49-181-255-194.pa.nsw.optusnet.com.au [49.181.255.194]) by mail105.syd.optusnet.com.au (Postfix) with ESMTPS id 8DC5836277D for ; Fri, 6 Sep 2019 10:05:56 +1000 (AEST) Received: from discord.disaster.area ([192.168.253.110]) by dread.disaster.area with esmtp (Exim 4.92) (envelope-from ) id 1i61lD-0003ZL-EU for linux-xfs@vger.kernel.org; Fri, 06 Sep 2019 10:05:55 +1000 Received: from dave by discord.disaster.area with local (Exim 4.92) (envelope-from ) id 1i61lD-0001mQ-CZ for linux-xfs@vger.kernel.org; Fri, 06 Sep 2019 10:05:55 +1000 From: Dave Chinner To: linux-xfs@vger.kernel.org Subject: [PATCH 1/8] xfs: push the AIL in xlog_grant_head_wake Date: Fri, 6 Sep 2019 10:05:46 +1000 Message-Id: <20190906000553.6740-2-david@fromorbit.com> X-Mailer: git-send-email 2.23.0.rc1 In-Reply-To: <20190906000553.6740-1-david@fromorbit.com> References: <20190906000553.6740-1-david@fromorbit.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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=eu_1AKrEyvAHeJIYhIUA: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 | 29 ++++++++++++++++++++++++++++- 1 file changed, 28 insertions(+), 1 deletion(-) diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c index b159a9e9fef0..c2862b1a2780 100644 --- a/fs/xfs/xfs_log.c +++ b/fs/xfs/xfs_log.c @@ -214,15 +214,42 @@ 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 at the last AIL push target calculation resulted in + * limiting the target to the log head (l_last_sync_lsn) at the + * time. This may not reflect where the log head is now as the + * CIL checkpoints may have completed. + * + * Hence when we are woken here, it may be that the head of the + * log that has moved rather than the tail. As the tail didn't + * move, there still won't be space available for the + * reservation we require. However, if the AIL has already + * pushed to the target defined by the old log head location, we + * will hang here waiting for something else to update the AIL + * push target. + * + * Therefore, 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 both 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; -- 2.23.0.rc1