From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f173.google.com ([209.85.192.173]:33500 "EHLO mail-pf0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750971AbcISRsw (ORCPT ); Mon, 19 Sep 2016 13:48:52 -0400 Received: by mail-pf0-f173.google.com with SMTP id 21so42452190pfy.0 for ; Mon, 19 Sep 2016 10:48:51 -0700 (PDT) Date: Mon, 19 Sep 2016 10:48:49 -0700 From: Omar Sandoval To: Alexander Gordeev Cc: linux-kernel@vger.kernel.org, linux-block@vger.kernel.org Subject: Re: [PATCH 04/14] blk-mq: Do not limit number of queues to 'nr_cpu_ids' in allocations Message-ID: <20160919174849.GA21803@vader> References: <9bb584d504bc2f8ef9d66822e68f082ee9a74ded.1474183901.git.agordeev@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <9bb584d504bc2f8ef9d66822e68f082ee9a74ded.1474183901.git.agordeev@redhat.com> Sender: linux-block-owner@vger.kernel.org List-Id: linux-block@vger.kernel.org On Sun, Sep 18, 2016 at 09:37:14AM +0200, Alexander Gordeev wrote: > Currently maximum number of used hardware queues is limited to > number of CPUs in the system. However, using 'nr_cpu_ids' as > the limit for (de-)allocations of data structures instead of > existing data structures' counters (a) worsens readability and > (b) leads to unused memory when number of hardware queues is > less than number of CPUs. > > CC: linux-block@vger.kernel.org > Signed-off-by: Alexander Gordeev > --- > block/blk-mq.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/block/blk-mq.c b/block/blk-mq.c > index 276ec7b..2c77b68 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -2054,8 +2054,8 @@ struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set, > if (!q->queue_ctx) > goto err_exit; > > - q->queue_hw_ctx = kzalloc_node(nr_cpu_ids * sizeof(*(q->queue_hw_ctx)), > - GFP_KERNEL, set->numa_node); > + q->queue_hw_ctx = kzalloc_node(set->nr_hw_queues * > + sizeof(*(q->queue_hw_ctx)), GFP_KERNEL, set->numa_node); > if (!q->queue_hw_ctx) > goto err_percpu; > > @@ -2319,7 +2319,7 @@ int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set) > if (set->nr_hw_queues > nr_cpu_ids) > set->nr_hw_queues = nr_cpu_ids; > > - set->tags = kzalloc_node(nr_cpu_ids * sizeof(struct blk_mq_tags *), > + set->tags = kzalloc_node(set->nr_hw_queues * sizeof(*set->tags), > GFP_KERNEL, set->numa_node); > if (!set->tags) > return -ENOMEM; > @@ -2360,7 +2360,7 @@ void blk_mq_free_tag_set(struct blk_mq_tag_set *set) > { > int i; > > - for (i = 0; i < nr_cpu_ids; i++) { > + for (i = 0; i < set->nr_hw_queues; i++) { > if (set->tags[i]) > blk_mq_free_rq_map(set, set->tags[i], i); > } I don't think this is safe since we might increase the number of hardware queues (blk_mq_update_nr_hw_queues()). -- Omar