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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,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 687F6C433E9 for ; Thu, 28 Jan 2021 04:42:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 29A8264DDB for ; Thu, 28 Jan 2021 04:42:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231147AbhA1Eml (ORCPT ); Wed, 27 Jan 2021 23:42:41 -0500 Received: from mail108.syd.optusnet.com.au ([211.29.132.59]:39221 "EHLO mail108.syd.optusnet.com.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231148AbhA1Emk (ORCPT ); Wed, 27 Jan 2021 23:42:40 -0500 Received: from dread.disaster.area (pa49-181-52-82.pa.nsw.optusnet.com.au [49.181.52.82]) by mail108.syd.optusnet.com.au (Postfix) with ESMTPS id 7A6461AD6C1 for ; Thu, 28 Jan 2021 15:41:57 +1100 (AEDT) Received: from discord.disaster.area ([192.168.253.110]) by dread.disaster.area with esmtp (Exim 4.92.3) (envelope-from ) id 1l4z80-003F5O-Jx for linux-xfs@vger.kernel.org; Thu, 28 Jan 2021 15:41:56 +1100 Received: from dave by discord.disaster.area with local (Exim 4.94) (envelope-from ) id 1l4z80-003NuJ-CG for linux-xfs@vger.kernel.org; Thu, 28 Jan 2021 15:41:56 +1100 From: Dave Chinner To: linux-xfs@vger.kernel.org Subject: [PATCH 5/5] xfs: reduce buffer log item shadow allocations Date: Thu, 28 Jan 2021 15:41:54 +1100 Message-Id: <20210128044154.806715-6-david@fromorbit.com> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20210128044154.806715-1-david@fromorbit.com> References: <20210128044154.806715-1-david@fromorbit.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Optus-CM-Score: 0 X-Optus-CM-Analysis: v=2.3 cv=Ubgvt5aN c=1 sm=1 tr=0 cx=a_idp_d a=7pwokN52O8ERr2y46pWGmQ==:117 a=7pwokN52O8ERr2y46pWGmQ==:17 a=IkcTkHD0fZMA:10 a=EmqxpYm9HcoA:10 a=20KFwNOVAAAA:8 a=fG2ZNbid02WDS2EagfEA:9 a=QEXdDO2ut3YA:10 Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org From: Dave Chinner When we modify btrees repeatedly, we regularly increase the size of the logged region by a single chunk at a time (per transaction commit). This results in the CIL formatting code having to reallocate the log vector buffer every time the buffer dirty region grows. Hence over a typical 4kB btree buffer, we might grow the log vector 4096/128 = 32x over a short period where we repeatedly add or remove records to/from the buffer over a series of running transaction. This means we are doing 32 memory allocations and frees over this time during a performance critical path in the journal. The amount of space tracked in the CIL for the object is calculated during the ->iop_format() call for the buffer log item, but the buffer memory allocated for it is calculated by the ->iop_size() call. The size callout determines the size of the buffer, the format call determines the space used in the buffer. Hence we can oversize the buffer space required in the size calculation without impacting the amount of space used and accounted to the CIL for the changes being logged. This allows us to reduce the number of allocations by rounding up the buffer size to allow for future growth. This can safe a substantial amount of CPU time in this path: - 46.52% 2.02% [kernel] [k] xfs_log_commit_cil - 44.49% xfs_log_commit_cil - 30.78% _raw_spin_lock - 30.75% do_raw_spin_lock 30.27% __pv_queued_spin_lock_slowpath (oh, ouch!) .... - 1.05% kmem_alloc_large - 1.02% kmem_alloc 0.94% __kmalloc This overhead here us what this patch is aimed at. After: - 0.76% kmem_alloc_large ▒ - 0.75% kmem_alloc ▒ 0.70% __kmalloc ▒ Signed-off-by: Dave Chinner --- fs/xfs/xfs_buf_item.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/fs/xfs/xfs_buf_item.c b/fs/xfs/xfs_buf_item.c index 17960b1ce5ef..0628a65d9c55 100644 --- a/fs/xfs/xfs_buf_item.c +++ b/fs/xfs/xfs_buf_item.c @@ -142,6 +142,7 @@ xfs_buf_item_size( { struct xfs_buf_log_item *bip = BUF_ITEM(lip); int i; + int bytes; ASSERT(atomic_read(&bip->bli_refcount) > 0); if (bip->bli_flags & XFS_BLI_STALE) { @@ -173,7 +174,7 @@ xfs_buf_item_size( } /* - * the vector count is based on the number of buffer vectors we have + * The vector count is based on the number of buffer vectors we have * dirty bits in. This will only be greater than one when we have a * compound buffer with more than one segment dirty. Hence for compound * buffers we need to track which segment the dirty bits correspond to, @@ -181,10 +182,18 @@ xfs_buf_item_size( * count for the extra buf log format structure that will need to be * written. */ + bytes = 0; for (i = 0; i < bip->bli_format_count; i++) { xfs_buf_item_size_segment(bip, &bip->bli_formats[i], - nvecs, nbytes); + nvecs, &bytes); } + + /* + * Round up the buffer size required to minimise the number of memory + * allocations that need to be done as this item grows when relogged by + * repeated modifications. + */ + *nbytes = round_up(bytes, 512); trace_xfs_buf_item_size(bip); } -- 2.28.0