From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757582AbaLIP7X (ORCPT ); Tue, 9 Dec 2014 10:59:23 -0500 Received: from xavier.telenet-ops.be ([195.130.132.52]:36196 "EHLO xavier.telenet-ops.be" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754402AbaLIP7W (ORCPT ); Tue, 9 Dec 2014 10:59:22 -0500 Message-ID: <54871C59.3050903@acm.org> Date: Tue, 09 Dec 2014 16:59:21 +0100 From: Bart Van Assche User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0 MIME-Version: 1.0 To: Jens Axboe CC: Christoph Hellwig , Robert Elliott , Ming Lei , Alexander Gordeev , linux-kernel Subject: [PATCH 5/6] blk-mq: Use all available hardware queues References: <54871BD0.8020305@acm.org> In-Reply-To: <54871BD0.8020305@acm.org> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Suppose that a system has two CPU sockets, three cores per socket, that it does not support hyperthreading and that four hardware queues are provided by a block driver. With the current algorithm this will lead to the following assignment of CPU cores to hardware queues: HWQ 0: 0 1 HWQ 1: 2 3 HWQ 2: 4 5 HWQ 3: (none) This patch changes the queue assignment into: HWQ 0: 0 1 HWQ 1: 2 HWQ 2: 3 4 HWQ 3: 5 In other words, this patch has the following three effects: - All four hardware queues are used instead of only three. - CPU cores are spread more evenly over hardware queues. For the above example the range of the number of CPU cores associated with a single HWQ is reduced from [0..2] to [1..2]. - If the number of HWQ's is a multiple of the number of CPU sockets it is now guaranteed that all CPU cores associated with a single HWQ reside on the same CPU socket. Signed-off-by: Bart Van Assche Reviewed-by: Sagi Grimberg Cc: Jens Axboe Cc: Christoph Hellwig Cc: Ming Lei Cc: Alexander Gordeev --- block/blk-mq-cpumap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/block/blk-mq-cpumap.c b/block/blk-mq-cpumap.c index 1065d7c..8e56455 100644 --- a/block/blk-mq-cpumap.c +++ b/block/blk-mq-cpumap.c @@ -17,7 +17,7 @@ static int cpu_to_queue_index(unsigned int nr_cpus, unsigned int nr_queues, const int cpu) { - return cpu / ((nr_cpus + nr_queues - 1) / nr_queues); + return cpu * nr_queues / nr_cpus; } static int get_first_sibling(unsigned int cpu) -- 2.1.2