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Message-ID: <20231211065323.GB4977@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net>
Date: Sun, 10 Dec 2023 22:53:23 -0800
From: Souradeep Chakrabarti <schakrabarti@...ux.microsoft.com>
To: Yury Norov <yury.norov@...il.com>
Cc: kys@...rosoft.com, haiyangz@...rosoft.com, wei.liu@...nel.org,
decui@...rosoft.com, davem@...emloft.net, edumazet@...gle.com,
kuba@...nel.org, pabeni@...hat.com, longli@...rosoft.com,
leon@...nel.org, cai.huoqing@...ux.dev,
ssengar@...ux.microsoft.com, vkuznets@...hat.com,
tglx@...utronix.de, linux-hyperv@...r.kernel.org,
netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-rdma@...r.kernel.org, schakrabarti@...rosoft.com,
paulros@...rosoft.com
Subject: Re: [PATCH V5 net-next] net: mana: Assigning IRQ affinity on HT cores
On Fri, Dec 08, 2023 at 01:53:51PM -0800, Yury Norov wrote:
> Few more nits
>
> On Fri, Dec 08, 2023 at 06:03:40AM -0800, Yury Norov wrote:
> > On Fri, Dec 08, 2023 at 02:02:34AM -0800, Souradeep Chakrabarti wrote:
> > > Existing MANA design assigns IRQ to every CPU, including sibling
> > > hyper-threads. This may cause multiple IRQs to be active simultaneously
> > > in the same core and may reduce the network performance with RSS.
> >
> > Can you add an IRQ distribution diagram to compare before/after
> > behavior, similarly to what I did in the other email?
> >
> > > Improve the performance by assigning IRQ to non sibling CPUs in local
> > > NUMA node. The performance improvement we are getting using ntttcp with
> > > following patch is around 15 percent with existing design and approximately
> > > 11 percent, when trying to assign one IRQ in each core across NUMA nodes,
> > > if enough cores are present.
> >
> > How did you measure it? In the other email you said you used perf, can
> > you show your procedure in details?
> >
> > > Suggested-by: Yury Norov <yury.norov@...li.com>
> > > Signed-off-by: Souradeep Chakrabarti <schakrabarti@...ux.microsoft.com>
> > > ---
> >
> > [...]
> >
> > > .../net/ethernet/microsoft/mana/gdma_main.c | 92 +++++++++++++++++--
> > > 1 file changed, 83 insertions(+), 9 deletions(-)
> > >
> > > diff --git a/drivers/net/ethernet/microsoft/mana/gdma_main.c b/drivers/net/ethernet/microsoft/mana/gdma_main.c
> > > index 6367de0c2c2e..18e8908c5d29 100644
> > > --- a/drivers/net/ethernet/microsoft/mana/gdma_main.c
> > > +++ b/drivers/net/ethernet/microsoft/mana/gdma_main.c
> > > @@ -1243,15 +1243,56 @@ void mana_gd_free_res_map(struct gdma_resource *r)
> > > r->size = 0;
> > > }
> > >
> > > +static int irq_setup(int *irqs, int nvec, int start_numa_node)
> > > +{
> > > + int w, cnt, cpu, err = 0, i = 0;
> > > + int next_node = start_numa_node;
> >
> > What for this?
> >
> > > + const struct cpumask *next, *prev = cpu_none_mask;
> > > + cpumask_var_t curr, cpus;
> > > +
> > > + if (!zalloc_cpumask_var(&curr, GFP_KERNEL)) {
>
> alloc_cpumask_var() here and below, because you initialize them by
> copying
I have used zalloc here as prev gets initialized after the first hop, before that
it may contain unwanted values, which may impact cpumask_andnot(curr, next, prev).
Regarding curr I will change it to alloc_cpumask_var().
Please let me know if that sounds right.
>
> > > + err = -ENOMEM;
> > > + return err;
> > > + }
> > > + if (!zalloc_cpumask_var(&cpus, GFP_KERNEL)) {
> >
> > free(curr);
> >
> > > + err = -ENOMEM;
> > > + return err;
> > > + }
> > > +
> > > + rcu_read_lock();
> > > + for_each_numa_hop_mask(next, next_node) {
> > > + cpumask_andnot(curr, next, prev);
> > > + for (w = cpumask_weight(curr), cnt = 0; cnt < w; ) {
>
> OK, if you can't increment inside for-loop, I'd switch it to a
> while-loop:
> w = cpumask_weight(curr);
> cnt = 0;
>
Thanks will change it to while loop.
> while (cnt < w) {
>
> > > + cpumask_copy(cpus, curr);
> > > + for_each_cpu(cpu, cpus) {
> > > + irq_set_affinity_and_hint(irqs[i], topology_sibling_cpumask(cpu));
> > > + if (++i == nvec)
> > > + goto done;
> >
> > Think what if you're passed with irq_setup(NULL, 0, 0).
> > That's why I suggested to place this check at the beginning.
> >
> >
> > > + cpumask_andnot(cpus, cpus, topology_sibling_cpumask(cpu));
> > > + ++cnt;
> > > + }
> > > + }
> > > + prev = next;
> > > + }
>
> Don't hesitate to add even more vertical spacing. It's like: "take a
> breath folks, this section is done". :)
>
Sure will add in next version.
> > > +done:
> > > + rcu_read_unlock();
> > > + free_cpumask_var(curr);
> > > + free_cpumask_var(cpus);
> > > + return err;
> > > +}
> > > +
> > > static int mana_gd_setup_irqs(struct pci_dev *pdev)
> > > {
> > > - unsigned int max_queues_per_port = num_online_cpus();
> > > struct gdma_context *gc = pci_get_drvdata(pdev);
> > > + unsigned int max_queues_per_port;
> > > struct gdma_irq_context *gic;
> > > unsigned int max_irqs, cpu;
> > > - int nvec, irq;
> > > + int start_irq_index = 1;
> > > + int nvec, *irqs, irq;
> > > int err, i = 0, j;
> > >
> > > + cpus_read_lock();
> > > + max_queues_per_port = num_online_cpus();
> > > if (max_queues_per_port > MANA_MAX_NUM_QUEUES)
> > > max_queues_per_port = MANA_MAX_NUM_QUEUES;
> > >
> > > @@ -1261,6 +1302,14 @@ static int mana_gd_setup_irqs(struct pci_dev *pdev)
> > > nvec = pci_alloc_irq_vectors(pdev, 2, max_irqs, PCI_IRQ_MSIX);
> > > if (nvec < 0)
> > > return nvec;
> > > + if (nvec <= num_online_cpus())
> > > + start_irq_index = 0;
> > > +
> > > + irqs = kmalloc_array((nvec - start_irq_index), sizeof(int), GFP_KERNEL);
> > > + if (!irqs) {
> > > + err = -ENOMEM;
> > > + goto free_irq_vector;
> > > + }
> > >
> > > gc->irq_contexts = kcalloc(nvec, sizeof(struct gdma_irq_context),
> > > GFP_KERNEL);
> > > @@ -1287,21 +1336,44 @@ static int mana_gd_setup_irqs(struct pci_dev *pdev)
> > > goto free_irq;
> > > }
> > >
> > > - err = request_irq(irq, mana_gd_intr, 0, gic->name, gic);
> > > - if (err)
> > > - goto free_irq;
> > > -
> > > - cpu = cpumask_local_spread(i, gc->numa_node);
> > > - irq_set_affinity_and_hint(irq, cpumask_of(cpu));
> > > + if (!i) {
> > > + err = request_irq(irq, mana_gd_intr, 0, gic->name, gic);
> > > + if (err)
> > > + goto free_irq;
> > > +
> > > + /* If number of IRQ is one extra than number of online CPUs,
> > > + * then we need to assign IRQ0 (hwc irq) and IRQ1 to
> > > + * same CPU.
> > > + * Else we will use different CPUs for IRQ0 and IRQ1.
> > > + * Also we are using cpumask_local_spread instead of
> > > + * cpumask_first for the node, because the node can be
> > > + * mem only.
> > > + */
> > > + if (start_irq_index) {
> > > + cpu = cpumask_local_spread(i, gc->numa_node);
> >
> > I already mentioned that: if i == 0, you don't need to spread, just
> > pick 1st cpu from node.
> >
> > > + irq_set_affinity_and_hint(irq, cpumask_of(cpu));
> > > + } else {
> > > + irqs[start_irq_index] = irq;
> > > + }
> > > + } else {
> > > + irqs[i - start_irq_index] = irq;
> > > + err = request_irq(irqs[i - start_irq_index], mana_gd_intr, 0,
> > > + gic->name, gic);
> > > + if (err)
> > > + goto free_irq;
> > > + }
> > > }
> > >
> > > + err = irq_setup(irqs, (nvec - start_irq_index), gc->numa_node);
> > > + if (err)
> > > + goto free_irq;
> > > err = mana_gd_alloc_res_map(nvec, &gc->msix_resource);
> > > if (err)
> > > goto free_irq;
> > >
> > > gc->max_num_msix = nvec;
> > > gc->num_msix_usable = nvec;
> > > -
> > > + cpus_read_unlock();
> > > return 0;
> > >
> > > free_irq:
> > > @@ -1314,8 +1386,10 @@ static int mana_gd_setup_irqs(struct pci_dev *pdev)
> > > }
> > >
> > > kfree(gc->irq_contexts);
> > > + kfree(irqs);
> > > gc->irq_contexts = NULL;
> > > free_irq_vector:
> > > + cpus_read_unlock();
> > > pci_free_irq_vectors(pdev);
> > > return err;
> > > }
> > > --
> > > 2.34.1
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