Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751822AbaBPLX6 (ORCPT ); Sun, 16 Feb 2014 06:23:58 -0500 Received: from mx1.redhat.com ([209.132.183.28]:9177 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751162AbaBPLX4 (ORCPT ); Sun, 16 Feb 2014 06:23:56 -0500 Date: Sun, 16 Feb 2014 12:25:29 +0100 From: Alexander Gordeev To: linux-kernel@vger.kernel.org Cc: Kent Overstreet , Peter Zijlstra , Jens Axboe , "Nicholas A. Bellinger" Subject: [PATCH 4/4] percpu_ida: Do not steal all remote CPU tags at once Message-ID: <20140216112528.GA13853@dhcp-26-207.brq.redhat.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When stealing from a remote CPU all available tags are moved from the remote CPU's cache to the stealing CPU's one. Since the best CPU to steal from is not selected the victim might actively performing IO and (as result of losing all local tags) a further cycle of cache rebouncing and/or stealing could be provoked. This update is an attempt to soften the described scenario and limit the number of tags to be stolen at once to the value of percpu_batch_size. Signed-off-by: Alexander Gordeev Cc: Kent Overstreet Cc: Peter Zijlstra Cc: Jens Axboe Cc: "Nicholas A. Bellinger" --- lib/percpu_ida.c | 18 ++++++++++-------- 1 files changed, 10 insertions(+), 8 deletions(-) diff --git a/lib/percpu_ida.c b/lib/percpu_ida.c index fad029c..b4c4cc7 100644 --- a/lib/percpu_ida.c +++ b/lib/percpu_ida.c @@ -84,20 +84,22 @@ static inline void steal_tags(struct percpu_ida *pool, pool->cpu_last_stolen = cpu; remote = per_cpu_ptr(pool->tag_cpu, cpu); - cpumask_clear_cpu(cpu, &pool->cpus_have_tags); - - if (remote == tags) + if (remote == tags) { + cpumask_clear_cpu(cpu, &pool->cpus_have_tags); continue; + } spin_lock(&remote->lock); if (remote->nr_free) { - memcpy(tags->freelist, - remote->freelist, - sizeof(unsigned) * remote->nr_free); + const struct percpu_ida *p = pool; + + move_tags(tags->freelist, &tags->nr_free, + remote->freelist, &remote->nr_free, + min(remote->nr_free, p->percpu_batch_size)); - tags->nr_free = remote->nr_free; - remote->nr_free = 0; + if (!remote->nr_free) + cpumask_clear_cpu(cpu, &pool->cpus_have_tags); } spin_unlock(&remote->lock); -- 1.7.7.6 -- Regards, Alexander Gordeev agordeev@redhat.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/