RE: [EXTERNAL] [PATCH 3/3] net: mana: add a function to spread IRQs per CPUs
From: Souradeep Chakrabarti
Date: Tue Dec 19 2023 - 05:19:09 EST
>-----Original Message-----
>From: Yury Norov <yury.norov@xxxxxxxxx>
>Sent: Monday, December 18, 2023 3:02 AM
>To: Souradeep Chakrabarti <schakrabarti@xxxxxxxxxxxxxxxxxxx>; KY Srinivasan
><kys@xxxxxxxxxxxxx>; Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>;
>wei.liu@xxxxxxxxxx; Dexuan Cui <decui@xxxxxxxxxxxxx>; davem@xxxxxxxxxxxxx;
>edumazet@xxxxxxxxxx; kuba@xxxxxxxxxx; pabeni@xxxxxxxxxx; Long Li
><longli@xxxxxxxxxxxxx>; yury.norov@xxxxxxxxx; leon@xxxxxxxxxx;
>cai.huoqing@xxxxxxxxx; ssengar@xxxxxxxxxxxxxxxxxxx; vkuznets@xxxxxxxxxx;
>tglx@xxxxxxxxxxxxx; linux-hyperv@xxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; linux-
>kernel@xxxxxxxxxxxxxxx; linux-rdma@xxxxxxxxxxxxxxx
>Cc: Souradeep Chakrabarti <schakrabarti@xxxxxxxxxxxxx>; Paul Rosswurm
><paulros@xxxxxxxxxxxxx>
>Subject: [EXTERNAL] [PATCH 3/3] net: mana: add a function to spread IRQs per
>CPUs
>
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>
>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%2Fall%2F20231211063726.GA4977%40linuxonhyperv3.guj3yctzbm1etfxqx2v
>ob5hsef.xx.internal.cloudapp.net%2F&data=05%7C02%7Cschakrabarti%40micros
>oft.com%7Ca385a5a5d661458219c208dbff47a7ab%7C72f988bf86f141af91ab2d7
>cd011db47%7C1%7C0%7C638384455520036393%7CUnknown%7CTWFpbGZsb3d
>8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%
>7C3000%7C%7C%7C&sdata=kzoalzSu6frB0GIaUM5VWsz04%2FsB%2FBdXwXKb26
>IhqkE%3D&reserved=0
>
>Signed-off-by: Yury Norov <yury.norov@xxxxxxxxx>
>Co-developed-by: Souradeep Chakrabarti <schakrabarti@xxxxxxxxxxxxxxxxxxx>
>---
> .../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) {
Make it 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));
Here do --weight, else this code will traverse the same node N^2 times, where each
node has N cpus .
>+ }
>+ }
>+ 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