Souradeep investigated that the driver performs faster if IRQs are
spread on CPUs with the following heuristics:
1. No more than one IRQ per CPU, if possible;
2. NUMA locality is the second priority;
3. Sibling dislocality is the last priority.
Let's consider this topology:
Node 0 1
Core 0 1 2 3
CPU 0 1 2 3 4 5 6 7
The most performant IRQ distribution based on the above topology
and heuristics may look like this:
IRQ Nodes Cores CPUs
0 1 0 0-1
1 1 1 2-3
2 1 0 0-1
3 1 1 2-3
4 2 2 4-5
5 2 3 6-7
6 2 2 4-5
7 2 3 6-7
The irq_setup() routine introduced in this patch leverages the
for_each_numa_hop_mask() iterator and assigns IRQs to sibling groups
as described above.
According to [1], for NUMA-aware but sibling-ignorant IRQ distribution
based on cpumask_local_spread() performance test results look like this:
./ntttcp -r -m 16
NTTTCP for Linux 1.4.0
---------------------------------------------------------
08:05:20 INFO: 17 threads created
08:05:28 INFO: Network activity progressing...
08:06:28 INFO: Test run completed.
08:06:28 INFO: Test cycle finished.
08:06:28 INFO: ##### Totals: #####
08:06:28 INFO: test duration :60.00 seconds
08:06:28 INFO: total bytes :630292053310
08:06:28 INFO: throughput :84.04Gbps
08:06:28 INFO: retrans segs :4
08:06:28 INFO: cpu cores :192
08:06:28 INFO: cpu speed :3799.725MHz
08:06:28 INFO: user :0.05%
08:06:28 INFO: system :1.60%
08:06:28 INFO: idle :96.41%
08:06:28 INFO: iowait :0.00%
08:06:28 INFO: softirq :1.94%
08:06:28 INFO: cycles/byte :2.50
08:06:28 INFO: cpu busy (all) :534.41%
For NUMA- and sibling-aware IRQ distribution, the same test works
15% faster:
./ntttcp -r -m 16
NTTTCP for Linux 1.4.0
---------------------------------------------------------
08:08:51 INFO: 17 threads created
08:08:56 INFO: Network activity progressing...
08:09:56 INFO: Test run completed.
08:09:56 INFO: Test cycle finished.
08:09:56 INFO: ##### Totals: #####
08:09:56 INFO: test duration :60.00 seconds
08:09:56 INFO: total bytes :741966608384
08:09:56 INFO: throughput :98.93Gbps
08:09:56 INFO: retrans segs :6
08:09:56 INFO: cpu cores :192
08:09:56 INFO: cpu speed :3799.791MHz
08:09:56 INFO: user :0.06%
08:09:56 INFO: system :1.81%
08:09:56 INFO: idle :96.18%
08:09:56 INFO: iowait :0.00%
08:09:56 INFO: softirq :1.95%
08:09:56 INFO: cycles/byte :2.25
08:09:56 INFO: cpu busy (all) :569.22%
[1] https://lore.kernel.org/all/20231211063726.GA4977@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net/
Signed-off-by: Yury Norov <yury.norov@gmail.com>
Co-developed-by: Souradeep Chakrabarti <schakrabarti@linux.microsoft.com>
---
.../net/ethernet/microsoft/mana/gdma_main.c | 28 +++++++++++++++++++
1 file changed, 28 insertions(+)
diff --git a/drivers/net/ethernet/microsoft/mana/gdma_main.c b/drivers/net/ethernet/microsoft/mana/gdma_main.c
index 6367de0c2c2e..11e64e42e3b2 100644
--- a/drivers/net/ethernet/microsoft/mana/gdma_main.c
+++ b/drivers/net/ethernet/microsoft/mana/gdma_main.c
@@ -1243,6 +1243,34 @@ void mana_gd_free_res_map(struct gdma_resource *r)
r->size = 0;
}
+static __maybe_unused int irq_setup(unsigned int *irqs, unsigned int len, int node)
+{
+ const struct cpumask *next, *prev = cpu_none_mask;
+ cpumask_var_t cpus __free(free_cpumask_var);
+ int cpu, weight;
+
+ if (!alloc_cpumask_var(&cpus, GFP_KERNEL))
+ return -ENOMEM;
+
+ rcu_read_lock();
+ for_each_numa_hop_mask(next, node) {
+ weight = cpumask_weight_andnot(next, prev);
+ while (weight-- > 0) {
+ cpumask_andnot(cpus, next, prev);
+ for_each_cpu(cpu, cpus) {
+ if (len-- == 0)
+ goto done;
+ irq_set_affinity_and_hint(*irqs++, topology_sibling_cpumask(cpu));
+ cpumask_andnot(cpus, cpus, topology_sibling_cpumask(cpu));
+ }
+ }
+ prev = next;
+ }
+done:
+ rcu_read_unlock();
+ return 0;
+}
+
static int mana_gd_setup_irqs(struct pci_dev *pdev)
{
unsigned int max_queues_per_port = num_online_cpus();
--
2.40.1
On 12/17/2023 1:32 PM, Yury Norov wrote:
> +static __maybe_unused int irq_setup(unsigned int *irqs, unsigned int len, int node)
> +{
> + const struct cpumask *next, *prev = cpu_none_mask;
> + cpumask_var_t cpus __free(free_cpumask_var);
> + int cpu, weight;
> +
> + if (!alloc_cpumask_var(&cpus, GFP_KERNEL))
> + return -ENOMEM;
> +
> + rcu_read_lock();
> + for_each_numa_hop_mask(next, node) {
> + weight = cpumask_weight_andnot(next, prev);
> + while (weight-- > 0) {
> + cpumask_andnot(cpus, next, prev);
> + for_each_cpu(cpu, cpus) {
> + if (len-- == 0)
> + goto done;
> + irq_set_affinity_and_hint(*irqs++, topology_sibling_cpumask(cpu));
> + cpumask_andnot(cpus, cpus, topology_sibling_cpumask(cpu));
> + }
> + }
> + prev = next;
> + }
> +done:
> + rcu_read_unlock();
> + return 0;
> +}
> +
You're adding a function here but its not called and even marked as
__maybe_unused?
> static int mana_gd_setup_irqs(struct pci_dev *pdev)
> {
> unsigned int max_queues_per_port = num_online_cpus();
On Mon, Dec 18, 2023 at 01:17:53PM -0800, Jacob Keller wrote:
>
>
> On 12/17/2023 1:32 PM, Yury Norov wrote:
> > +static __maybe_unused int irq_setup(unsigned int *irqs, unsigned int len, int node)
> > +{
> > + const struct cpumask *next, *prev = cpu_none_mask;
> > + cpumask_var_t cpus __free(free_cpumask_var);
> > + int cpu, weight;
> > +
> > + if (!alloc_cpumask_var(&cpus, GFP_KERNEL))
> > + return -ENOMEM;
> > +
> > + rcu_read_lock();
> > + for_each_numa_hop_mask(next, node) {
> > + weight = cpumask_weight_andnot(next, prev);
> > + while (weight-- > 0) {
> > + cpumask_andnot(cpus, next, prev);
> > + for_each_cpu(cpu, cpus) {
> > + if (len-- == 0)
> > + goto done;
> > + irq_set_affinity_and_hint(*irqs++, topology_sibling_cpumask(cpu));
> > + cpumask_andnot(cpus, cpus, topology_sibling_cpumask(cpu));
> > + }
> > + }
> > + prev = next;
> > + }
> > +done:
> > + rcu_read_unlock();
> > + return 0;
> > +}
> > +
>
> You're adding a function here but its not called and even marked as
> __maybe_unused?
I expect that Souradeep would build his driver improvement on top of
this function. cpumask API is somewhat tricky to use it properly here,
so this is an attempt help him, instead of moving back and forth on
review.
Sorry, I had to be more explicit.
Thanks,
Yury
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