From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 32DB019922D; Thu, 6 Jun 2024 14:13:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717683181; cv=none; b=ilaAXmRigq4b9yZYcvIYygbimE5C+/Xh4Z9ipOyecMtqeKa9+6TKFe/dxfPLKFuruAOTpAfJYO0Jd3WS+SPplIjgpc9DG4hwKuTYUZh0ASRsx67kbWkcn2snPelmi0WAfcgiiw2xvbs62gsz5eQ6n8Oza8UzN8zGYaVJEnW2W14= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717683181; c=relaxed/simple; bh=kE9iYZSrxeJTNyBmvGt+YHzrEPbDQNyHW0cRBPpxOJ4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ZLUzX1o0191bZY5irw+yiwCLo7+6XB6kazy2DCRaz1DdIOLnE3gLpb9Pg844NL8HgNc1CN0eUY0O5ZsGo9ae4nfektGJ+UgMFAacAfPSZb8RQtwYPt5/pCzwfHsmqzhJ6foVh3vjHg4a8k6RVPNIJFtYOagNA4MR+LKvxR2FqEw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=UeuqO8sn; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="UeuqO8sn" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 12863C32781; Thu, 6 Jun 2024 14:13:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1717683181; bh=kE9iYZSrxeJTNyBmvGt+YHzrEPbDQNyHW0cRBPpxOJ4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=UeuqO8snpfrIgKPKvFDpAq23XYQFJEdknbAv9bF2qGdCEbKwQkgS4QYiaZ7rl7mGO antko5MjoFj397DAxMPkohEcIwpX968VAzp2dXruMKF7+ygolihlMf8Vv52bVYaGRA pCNByfyBpW5PQDZdTQnGl6IsGNgMoVOI89UxKf0A= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Yu Kuai , Jens Axboe , Sasha Levin Subject: [PATCH 6.6 125/744] block: support to account io_ticks precisely Date: Thu, 6 Jun 2024 15:56:37 +0200 Message-ID: <20240606131736.427046096@linuxfoundation.org> X-Mailer: git-send-email 2.45.2 In-Reply-To: <20240606131732.440653204@linuxfoundation.org> References: <20240606131732.440653204@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Yu Kuai [ Upstream commit 99dc422335d8b2bd4d105797241d3e715bae90e9 ] Currently, io_ticks is accounted based on sampling, specifically update_io_ticks() will always account io_ticks by 1 jiffies from bdev_start_io_acct()/blk_account_io_start(), and the result can be inaccurate, for example(HZ is 250): Test script: fio -filename=/dev/sda -bs=4k -rw=write -direct=1 -name=test -thinktime=4ms Test result: util is about 90%, while the disk is really idle. This behaviour is introduced by commit 5b18b5a73760 ("block: delete part_round_stats and switch to less precise counting"), however, there was a key point that is missed that this patch also improve performance a lot: Before the commit: part_round_stats: if (part->stamp != now) stats |= 1; part_in_flight() -> there can be lots of task here in 1 jiffies. part_round_stats_single() __part_stat_add() part->stamp = now; After the commit: update_io_ticks: stamp = part->bd_stamp; if (time_after(now, stamp)) if (try_cmpxchg()) __part_stat_add() -> only one task can reach here in 1 jiffies. Hence in order to account io_ticks precisely, we only need to know if there are IO inflight at most once in one jiffies. Noted that for rq-based device, iterating tags should not be used here because 'tags->lock' is grabbed in blk_mq_find_and_get_req(), hence part_stat_lock_inc/dec() and part_in_flight() is used to trace inflight. The additional overhead is quite little: - per cpu add/dec for each IO for rq-based device; - per cpu sum for each jiffies; And it's verified by null-blk that there are no performance degration under heavy IO pressure. Fixes: 5b18b5a73760 ("block: delete part_round_stats and switch to less precise counting") Signed-off-by: Yu Kuai Link: https://lore.kernel.org/r/20240509123717.3223892-2-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- block/blk-core.c | 9 +++++---- block/blk-merge.c | 2 ++ block/blk-mq.c | 4 ++++ block/blk.h | 1 + block/genhd.c | 2 +- 5 files changed, 13 insertions(+), 5 deletions(-) diff --git a/block/blk-core.c b/block/blk-core.c index a3726d8cf8738..bf058cea9016a 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -950,10 +950,11 @@ void update_io_ticks(struct block_device *part, unsigned long now, bool end) unsigned long stamp; again: stamp = READ_ONCE(part->bd_stamp); - if (unlikely(time_after(now, stamp))) { - if (likely(try_cmpxchg(&part->bd_stamp, &stamp, now))) - __part_stat_add(part, io_ticks, end ? now - stamp : 1); - } + if (unlikely(time_after(now, stamp)) && + likely(try_cmpxchg(&part->bd_stamp, &stamp, now)) && + (end || part_in_flight(part))) + __part_stat_add(part, io_ticks, now - stamp); + if (part->bd_partno) { part = bdev_whole(part); goto again; diff --git a/block/blk-merge.c b/block/blk-merge.c index 65e75efa9bd36..07bf758c523a9 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -783,6 +783,8 @@ static void blk_account_io_merge_request(struct request *req) if (blk_do_io_stat(req)) { part_stat_lock(); part_stat_inc(req->part, merges[op_stat_group(req_op(req))]); + part_stat_local_dec(req->part, + in_flight[op_is_write(req_op(req))]); part_stat_unlock(); } } diff --git a/block/blk-mq.c b/block/blk-mq.c index 257b0addd47e5..4c91889affa7c 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -994,6 +994,8 @@ static inline void blk_account_io_done(struct request *req, u64 now) update_io_ticks(req->part, jiffies, true); part_stat_inc(req->part, ios[sgrp]); part_stat_add(req->part, nsecs[sgrp], now - req->start_time_ns); + part_stat_local_dec(req->part, + in_flight[op_is_write(req_op(req))]); part_stat_unlock(); } } @@ -1016,6 +1018,8 @@ static inline void blk_account_io_start(struct request *req) part_stat_lock(); update_io_ticks(req->part, jiffies, false); + part_stat_local_inc(req->part, + in_flight[op_is_write(req_op(req))]); part_stat_unlock(); } } diff --git a/block/blk.h b/block/blk.h index 08a358bc0919e..67915b04b3c17 100644 --- a/block/blk.h +++ b/block/blk.h @@ -344,6 +344,7 @@ static inline bool blk_do_io_stat(struct request *rq) } void update_io_ticks(struct block_device *part, unsigned long now, bool end); +unsigned int part_in_flight(struct block_device *part); static inline void req_set_nomerge(struct request_queue *q, struct request *req) { diff --git a/block/genhd.c b/block/genhd.c index 2ef1e08d70ecd..33b1ebf6ef82d 100644 --- a/block/genhd.c +++ b/block/genhd.c @@ -118,7 +118,7 @@ static void part_stat_read_all(struct block_device *part, } } -static unsigned int part_in_flight(struct block_device *part) +unsigned int part_in_flight(struct block_device *part) { unsigned int inflight = 0; int cpu; -- 2.43.0