From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C78B8C32750 for ; Tue, 13 Aug 2019 07:41:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 94A4720679 for ; Tue, 13 Aug 2019 07:41:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727786AbfHMHlZ (ORCPT ); Tue, 13 Aug 2019 03:41:25 -0400 Received: from mx1.redhat.com ([209.132.183.28]:58234 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725981AbfHMHlY (ORCPT ); Tue, 13 Aug 2019 03:41:24 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id D49C8308A968; Tue, 13 Aug 2019 07:41:23 +0000 (UTC) Received: from ming.t460p (ovpn-8-25.pek2.redhat.com [10.72.8.25]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 2DBD91710C; Tue, 13 Aug 2019 07:41:16 +0000 (UTC) Date: Tue, 13 Aug 2019 15:41:14 +0800 From: Ming Lei To: Keith Busch Cc: Jens Axboe , linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, Thomas Gleixner , Christoph Hellwig , Jon Derrick Subject: Re: [PATCH V2 2/3] genirq/affinity: Spread vectors on node according to nr_cpu ratio Message-ID: <20190813074112.GA8610@ming.t460p> References: <20190812095709.25623-1-ming.lei@redhat.com> <20190812095709.25623-3-ming.lei@redhat.com> <20190812152718.GA32550@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190812152718.GA32550@localhost.localdomain> User-Agent: Mutt/1.11.3 (2019-02-01) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.41]); Tue, 13 Aug 2019 07:41:24 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 12, 2019 at 09:27:18AM -0600, Keith Busch wrote: > On Mon, Aug 12, 2019 at 05:57:08PM +0800, Ming Lei wrote: > > Now __irq_build_affinity_masks() spreads vectors evenly per node, and > > all vectors may not be spread in case that each numa node has different > > CPU number, then the following warning in irq_build_affinity_masks() can > > be triggered: > > > > if (nr_present < numvecs) > > WARN_ON(nr_present + nr_others < numvecs); > > > > Improve current spreading algorithm by assigning vectors according to > > the ratio of node's nr_cpu to nr_remaining_cpus, meantime running the > > assignment from smaller nodes to bigger nodes to guarantee that every > > active node gets allocated at least one vector, then we can avoid > > cross-node spread. > > > > Meantime the reported warning can be fixed. > > > > Another big goodness is that the spread approach becomes more fair if > > node has different CPU number. > > > > For example, on the following machine: > > [root@ktest-01 ~]# lscpu > > ... > > CPU(s): 16 > > On-line CPU(s) list: 0-15 > > Thread(s) per core: 1 > > Core(s) per socket: 8 > > Socket(s): 2 > > NUMA node(s): 2 > > ... > > NUMA node0 CPU(s): 0,1,3,5-9,11,13-15 > > NUMA node1 CPU(s): 2,4,10,12 > > > > When driver requests to allocate 8 vectors, the following spread can > > be got: > > irq 31, cpu list 2,4 > > irq 32, cpu list 10,12 > > irq 33, cpu list 0-1 > > irq 34, cpu list 3,5 > > irq 35, cpu list 6-7 > > irq 36, cpu list 8-9 > > irq 37, cpu list 11,13 > > irq 38, cpu list 14-15 > > > > Without this patch, kernel warning is triggered on above situation, and > > allocation result was supposed to be 4 vectors for each node. > > > > Cc: Christoph Hellwig > > Cc: Keith Busch > > Cc: linux-nvme@lists.infradead.org, > > Cc: Jon Derrick > > Cc: Jens Axboe > > Reported-by: Jon Derrick > > Signed-off-by: Ming Lei > > --- > > kernel/irq/affinity.c | 141 +++++++++++++++++++++++++++++++++++------- > > 1 file changed, 117 insertions(+), 24 deletions(-) > > > > diff --git a/kernel/irq/affinity.c b/kernel/irq/affinity.c > > index c7cca942bd8a..927dcbe80482 100644 > > --- a/kernel/irq/affinity.c > > +++ b/kernel/irq/affinity.c > > @@ -7,6 +7,7 @@ > > #include > > #include > > #include > > +#include > > > > static void irq_spread_init_one(struct cpumask *irqmsk, struct cpumask *nmsk, > > unsigned int cpus_per_vec) > > @@ -94,6 +95,87 @@ static int get_nodes_in_cpumask(cpumask_var_t *node_to_cpumask, > > return nodes; > > } > > > > +struct node_nr_vectors { > > + unsigned n; > > + > > + union { > > + unsigned nvectors; > > + unsigned ncpus; > > + }; > > +}; > > + > > +static int ncpus_cmp_func(const void *l, const void *r) > > +{ > > + const struct node_nr_vectors *ln = l; > > + const struct node_nr_vectors *rn = r; > > + > > + if (ln->ncpus < rn->ncpus) > > + return -1; > > + if (ln->ncpus > rn->ncpus) > > + return 1; > > + return 0; > > You can collapse these to one line: > > return ln->ncpus - rn->ncpus; OK. > > > +} > > + > > +static void alloc_nodes_vectors(unsigned int numvecs, > > + const cpumask_var_t *node_to_cpumask, > > + const struct cpumask *cpu_mask, > > + const nodemask_t nodemsk, > > + struct cpumask *nmsk, > > + struct node_nr_vectors *node_vectors) > > +{ > > + unsigned remaining_ncpus = 0; > > + unsigned n; > > + > > + for (n = 0; n < nr_node_ids; n++) { > > + node_vectors[n].n = n; > > + node_vectors[n].ncpus = UINT_MAX; > > + } > > + > > + for_each_node_mask(n, nodemsk) { > > + unsigned ncpus; > > + > > + cpumask_and(nmsk, cpu_mask, node_to_cpumask[n]); > > + ncpus = cpumask_weight(nmsk); > > + > > + if (!ncpus) > > + continue; > > + remaining_ncpus += ncpus; > > + node_vectors[n].ncpus = ncpus; > > + } > > + > > + sort(node_vectors, nr_node_ids, sizeof(node_vectors[0]), > > + ncpus_cmp_func, NULL); > > + > > + /* > > + * Allocate vectors for each node according to the ratio of this > > + * node's nr_cpus to remaining un-assigned ncpus. 'numvecs' is > > + * bigger than number of active numa nodes. Always start the > > + * allocation from the node with minimized nr_cpus. > > + * > > + * This way guarantees that each active node gets allocated at > > + * least one vector, and the theory is simple: over-allocation > > + * is only done when this node is assigned by one vector, so > > + * other nodes will be allocated >= 1 vector, since 'numvecs' is > > + * bigger than number of numa nodes. > > + */ > > + for (n = 0; n < nr_node_ids; n++) { > > + unsigned nvectors, ncpus; > > + > > + if (node_vectors[n].ncpus == UINT_MAX) > > + continue; > > + > > + WARN_ON_ONCE(numvecs == 0); > > + > > + ncpus = node_vectors[n].ncpus; > > + nvectors = max_t(unsigned, 1, > > + numvecs * ncpus / remaining_ncpus); > > + > > + node_vectors[n].nvectors = nvectors; > > + remaining_ncpus -= ncpus; > > + numvecs -= nvectors; > > + } > > This looks good to me. > > > +} > > + > > static int __irq_build_affinity_masks(unsigned int startvec, > > unsigned int numvecs, > > unsigned int firstvec, > > @@ -102,10 +184,11 @@ static int __irq_build_affinity_masks(unsigned int startvec, > > struct cpumask *nmsk, > > struct irq_affinity_desc *masks) > > { > > - unsigned int n, nodes, cpus_per_vec, extra_vecs, done = 0; > > + unsigned int i, n, nodes, cpus_per_vec, extra_vecs, done = 0; > > unsigned int last_affv = firstvec + numvecs; > > unsigned int curvec = startvec; > > nodemask_t nodemsk = NODE_MASK_NONE; > > + struct node_nr_vectors *node_vectors; > > > > if (!cpumask_weight(cpu_mask)) > > return 0; > > @@ -126,8 +209,23 @@ static int __irq_build_affinity_masks(unsigned int startvec, > > return numvecs; > > } > > > > - for_each_node_mask(n, nodemsk) { > > - unsigned int ncpus, v, vecs_to_assign, vecs_per_node; > > + node_vectors = kcalloc(nr_node_ids, > > + sizeof(struct node_nr_vectors), > > + GFP_KERNEL); > > + if (!node_vectors) > > + return 0; > > I think we need to get this -ENOMEM condition back to the caller and > have that condition handled. Good point. > > > @@ -165,13 +250,21 @@ static int __irq_build_affinity_masks(unsigned int startvec, > > } > > irq_spread_init_one(&masks[curvec].mask, nmsk, > > cpus_per_vec); > > + /* > > + * alloc_nodes_vectors() is intelligent enough to > > + * allocate vectors on all nodes, so wrapping > > + * shouldn't be triggered usually. However, if it > > + * happens when allocated vectors is bigger than > > + * node's CPU number becasue of round down, wraps > > + * to the first vector allocated for this node, then > > + * cross-node spread can be avoided. > > + */ > > + if (curvec >= last_affv) > > + curvec -= v; > > Could you explain again how this could happen? The round-down should mean we > apply a vector to more CPUs so that the number of vectors applied to a > node wthin the loop should never require wrapping to hit all those CPUs. > And if that's true, the check should probably be a warn because it > should never happen. You are right. We should simply spread from the 1st vector for this node if there is more vectors not done. > > In any case, if you can hit that condition where curvec >= last_affv, > the assignment to masks[curvec] just above may be out-of-bounds. Yeah, 'curvec >= last_affv' shouldn't be needed. Will fix them in V3. Thanks, Ming