Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753876AbdDDKF1 (ORCPT ); Tue, 4 Apr 2017 06:05:27 -0400 Received: from terminus.zytor.com ([65.50.211.136]:49777 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753276AbdDDKFV (ORCPT ); Tue, 4 Apr 2017 06:05:21 -0400 Date: Tue, 4 Apr 2017 03:03:47 -0700 From: tip-bot for Keith Busch Message-ID: Cc: tglx@linutronix.de, linux-kernel@vger.kernel.org, hpa@zytor.com, hch@lst.de, keith.busch@intel.com, mingo@kernel.org, sagi@grimberg.me Reply-To: keith.busch@intel.com, mingo@kernel.org, hch@lst.de, sagi@grimberg.me, tglx@linutronix.de, linux-kernel@vger.kernel.org, hpa@zytor.com In-Reply-To: <1491247553-7603-1-git-send-email-keith.busch@intel.com> References: <1491247553-7603-1-git-send-email-keith.busch@intel.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:irq/urgent] irq/affinity: Fix CPU spread for unbalanced nodes Git-Commit-ID: 7bf8222b9bd0ba867e18b7f4537b61ef2e92eee8 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3334 Lines: 91 Commit-ID: 7bf8222b9bd0ba867e18b7f4537b61ef2e92eee8 Gitweb: http://git.kernel.org/tip/7bf8222b9bd0ba867e18b7f4537b61ef2e92eee8 Author: Keith Busch AuthorDate: Mon, 3 Apr 2017 15:25:53 -0400 Committer: Thomas Gleixner CommitDate: Tue, 4 Apr 2017 11:57:28 +0200 irq/affinity: Fix CPU spread for unbalanced nodes The irq_create_affinity_masks routine is responsible for assigning a number of interrupt vectors to CPUs. The optimal assignemnet will spread requested vectors to all CPUs, with the fewest CPUs sharing a vector. The algorithm may fail to assign some vectors to any CPUs if a node's CPU count is lower than the average number of vectors per node. These vectors are unusable and create an un-optimal spread. Recalculate the number of vectors to assign at each node iteration by using the remaining number of vectors and nodes to be assigned, not exceeding the number of CPUs in that node. This will guarantee that every CPU is assigned at least one vector. Signed-off-by: Keith Busch Reviewed-by: Sagi Grimberg Reviewed-by: Christoph Hellwig Cc: linux-nvme@lists.infradead.org Link: http://lkml.kernel.org/r/1491247553-7603-1-git-send-email-keith.busch@intel.com Signed-off-by: Thomas Gleixner --- kernel/irq/affinity.c | 20 +++++++++++--------- 1 file changed, 11 insertions(+), 9 deletions(-) diff --git a/kernel/irq/affinity.c b/kernel/irq/affinity.c index 4544b11..dc52911 100644 --- a/kernel/irq/affinity.c +++ b/kernel/irq/affinity.c @@ -59,7 +59,7 @@ static int get_nodes_in_cpumask(const struct cpumask *mask, nodemask_t *nodemsk) struct cpumask * irq_create_affinity_masks(int nvecs, const struct irq_affinity *affd) { - int n, nodes, vecs_per_node, cpus_per_vec, extra_vecs, curvec; + int n, nodes, cpus_per_vec, extra_vecs, curvec; int affv = nvecs - affd->pre_vectors - affd->post_vectors; int last_affv = affv + affd->pre_vectors; nodemask_t nodemsk = NODE_MASK_NONE; @@ -94,19 +94,21 @@ irq_create_affinity_masks(int nvecs, const struct irq_affinity *affd) goto done; } - /* Spread the vectors per node */ - vecs_per_node = affv / nodes; - /* Account for rounding errors */ - extra_vecs = affv - (nodes * vecs_per_node); - for_each_node_mask(n, nodemsk) { - int ncpus, v, vecs_to_assign = vecs_per_node; + int ncpus, v, vecs_to_assign, vecs_per_node; + + /* Spread the vectors per node */ + vecs_per_node = (affv - curvec) / nodes; /* Get the cpus on this node which are in the mask */ cpumask_and(nmsk, cpu_online_mask, cpumask_of_node(n)); /* Calculate the number of cpus per vector */ ncpus = cpumask_weight(nmsk); + vecs_to_assign = min(vecs_per_node, ncpus); + + /* Account for rounding errors */ + extra_vecs = ncpus - vecs_to_assign; for (v = 0; curvec < last_affv && v < vecs_to_assign; curvec++, v++) { @@ -115,14 +117,14 @@ irq_create_affinity_masks(int nvecs, const struct irq_affinity *affd) /* Account for extra vectors to compensate rounding errors */ if (extra_vecs) { cpus_per_vec++; - if (!--extra_vecs) - vecs_per_node++; + --extra_vecs; } irq_spread_init_one(masks + curvec, nmsk, cpus_per_vec); } if (curvec >= last_affv) break; + --nodes; } done: