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Message-ID: <015401d41ea3$3ce8cfa0$b6ba6ee0$@opengridcomputing.com>
Date: Wed, 18 Jul 2018 09:25:54 -0500
From: "Steve Wise" <swise@...ngridcomputing.com>
To: "'Max Gurtovoy'" <maxg@...lanox.com>,
"'Sagi Grimberg'" <sagi@...mberg.me>,
"'Leon Romanovsky'" <leon@...nel.org>
Cc: "'Doug Ledford'" <dledford@...hat.com>,
"'Jason Gunthorpe'" <jgg@...lanox.com>,
"'RDMA mailing list'" <linux-rdma@...r.kernel.org>,
"'Saeed Mahameed'" <saeedm@...lanox.com>,
"'linux-netdev'" <netdev@...r.kernel.org>
Subject: RE: [PATCH mlx5-next] RDMA/mlx5: Don't use cached IRQ affinity mask
> -----Original Message-----
> From: Max Gurtovoy <maxg@...lanox.com>
> Sent: Wednesday, July 18, 2018 9:14 AM
> To: Sagi Grimberg <sagi@...mberg.me>; Steve Wise
> <swise@...ngridcomputing.com>; 'Leon Romanovsky' <leon@...nel.org>
> Cc: 'Doug Ledford' <dledford@...hat.com>; 'Jason Gunthorpe'
> <jgg@...lanox.com>; 'RDMA mailing list' <linux-rdma@...r.kernel.org>;
> 'Saeed Mahameed' <saeedm@...lanox.com>; 'linux-netdev'
> <netdev@...r.kernel.org>
> Subject: Re: [PATCH mlx5-next] RDMA/mlx5: Don't use cached IRQ affinity
> mask
>
>
>
> On 7/18/2018 2:38 PM, Sagi Grimberg wrote:
> >
> >>> IMO we must fulfil the user wish to connect to N queues and not reduce
> >>> it because of affinity overlaps. So in order to push Leon's patch we
> >>> must also fix the blk_mq_rdma_map_queues to do a best effort
> mapping
> >>> according the affinity and map the rest in naive way (in that way we
> >>> will *always* map all the queues).
> >>
> >> That is what I would expect also. For example, in my node, where
> >> there are
> >> 16 cpus, and 2 numa nodes, I observe much better nvmf IOPS
> performance by
> >> setting up my 16 driver completion event queues such that each is
> >> bound to a
> >> node-local cpu. So I end up with each nodel-local cpu having 2 queues
> >> bound
> >> to it. W/O adding support in iw_cxgb4 for ib_get_vector_affinity(),
> >> this
> >> works fine. I assumed adding ib_get_vector_affinity() would allow
> >> this to
> >> all "just work" by default, but I'm running into this connection failure
> >> issue.
> >>
> >> I don't understand exactly what the blk_mq layer is trying to do, but I
> >> assume it has ingress event queues and processing that it trying to align
> >> with the drivers ingress cq event handling, so everybody stays on the
> >> same
> >> cpu (or at least node). But something else is going on. Is there
> >> documentation on how this works somewhere?
> >
> > Does this (untested) patch help?
>
> I'm not sure (I'll test it tomorrow) because the issue is the unmapped
> queues and not the cpus.
> for example, if the affinity of q=6 and q=12 returned the same cpumask
> than q=6 will not be mapped and will fail to connect.
>
> > --
> > diff --git a/block/blk-mq-cpumap.c b/block/blk-mq-cpumap.c
> > index 3eb169f15842..dbe962cb537d 100644
> > --- a/block/blk-mq-cpumap.c
> > +++ b/block/blk-mq-cpumap.c
> > @@ -30,29 +30,34 @@ static int get_first_sibling(unsigned int cpu)
> > return cpu;
> > }
> >
> > -int blk_mq_map_queues(struct blk_mq_tag_set *set)
> > +void blk_mq_map_queue(struct blk_mq_tag_set *set, unsigned int cpu)
> > {
There is already a static inline function named blk_mq_map_queue() in block/blk-mq.h. Did you mean to replace that? Or is this just a function name conflict?
> > unsigned int *map = set->mq_map;
> > unsigned int nr_queues = set->nr_hw_queues;
> > - unsigned int cpu, first_sibling;
> > + unsigned int first_sibling;
> >
> > - for_each_possible_cpu(cpu) {
> > - /*
> > - * First do sequential mapping between CPUs and queues.
> > - * In case we still have CPUs to map, and we have some
> > number of
> > - * threads per cores then map sibling threads to the
> > same queue for
> > - * performace optimizations.
> > - */
> > - if (cpu < nr_queues) {
> > + /*
> > + * First do sequential mapping between CPUs and queues.
> > + * In case we still have CPUs to map, and we have some number of
> > + * threads per cores then map sibling threads to the same queue for
> > + * performace optimizations.
> > + */
> > + if (cpu < nr_queues) {
> > + map[cpu] = cpu_to_queue_index(nr_queues, cpu);
> > + } else {
> > + first_sibling = get_first_sibling(cpu);
> > + if (first_sibling == cpu)
> > map[cpu] = cpu_to_queue_index(nr_queues, cpu);
> > - } else {
> > - first_sibling = get_first_sibling(cpu);
> > - if (first_sibling == cpu)
> > - map[cpu] = cpu_to_queue_index(nr_queues,
> > cpu);
> > - else
> > - map[cpu] = map[first_sibling];
> > - }
> > + else
> > + map[cpu] = map[first_sibling];
> > }
> > +}
> > +EXPORT_SYMBOL_GPL(blk_mq_map_queue);
> > +
> > +int blk_mq_map_queues(struct blk_mq_tag_set *set)
> > +{
> > + for_each_possible_cpu(cpu)
> > + blk_mq_map_queue(set, cpu);
> >
> > return 0;
> > }
> > diff --git a/block/blk-mq-rdma.c b/block/blk-mq-rdma.c
> > index 996167f1de18..5e91789bea5b 100644
> > --- a/block/blk-mq-rdma.c
> > +++ b/block/blk-mq-rdma.c
> > @@ -35,6 +35,10 @@ int blk_mq_rdma_map_queues(struct
> blk_mq_tag_set *set,
> > const struct cpumask *mask;
> > unsigned int queue, cpu;
> >
> > + /* reset all to */
> > + for_each_possible_cpu(cpu)
> > + set->mq_map[cpu] = UINT_MAX;
> > +
> > for (queue = 0; queue < set->nr_hw_queues; queue++) {
> > mask = ib_get_vector_affinity(dev, first_vec + queue);
> > if (!mask)
> > @@ -44,6 +48,11 @@ int blk_mq_rdma_map_queues(struct
> blk_mq_tag_set *set,
> > set->mq_map[cpu] = queue;
> > }
> >
> > + for_each_possible_cpu(cpu) {
> > + if (set->mq_map[cpu] == UINT_MAX)
> > + blk_mq_map_queue(set, cpu);
> > + }
> > +
> > return 0;
> >
> > fallback:
> > diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
> > index e3147eb74222..7a9848a82475 100644
> > --- a/include/linux/blk-mq.h
> > +++ b/include/linux/blk-mq.h
> > @@ -283,6 +283,7 @@ int blk_mq_freeze_queue_wait_timeout(struct
> > request_queue *q,
> > unsigned long timeout);
> >
> > int blk_mq_map_queues(struct blk_mq_tag_set *set);
> > +void blk_mq_map_queue(struct blk_mq_tag_set *set, unsigned int cpu);
> > void blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, int
> > nr_hw_queues);
> >
> > void blk_mq_quiesce_queue_nowait(struct request_queue *q);
> > --
> >
> > It really is still a best effort thing...
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