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Message-ID: <ZXOQb+3R0YAT/rAm@yury-ThinkPad>
Date: Fri, 8 Dec 2023 13:53:51 -0800
From: Yury Norov <yury.norov@...il.com>
To: Souradeep Chakrabarti <schakrabarti@...ux.microsoft.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
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
> > + 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;
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". :)
> > +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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