On Thu, Nov 30, 2023 at 04:05:12AM -0800, Souradeep Chakrabarti wrote: > On Wed, Nov 29, 2023 at 06:16:17PM -0800, Yury Norov wrote: > > On Mon, Nov 27, 2023 at 09:36:38AM +0000, Souradeep Chakrabarti wrote: > > > > > > > > > >-----Original Message----- > > > >From: Jakub Kicinski <kuba@xxxxxxxxxx> > > > >Sent: Wednesday, November 22, 2023 5:19 AM > > > >To: Souradeep Chakrabarti <schakrabarti@xxxxxxxxxxxxxxxxxxx> > > > >Cc: KY Srinivasan <kys@xxxxxxxxxxxxx>; Haiyang Zhang > > > ><haiyangz@xxxxxxxxxxxxx>; wei.liu@xxxxxxxxxx; Dexuan Cui > > > ><decui@xxxxxxxxxxxxx>; davem@xxxxxxxxxxxxx; edumazet@xxxxxxxxxx; > > > >pabeni@xxxxxxxxxx; Long Li <longli@xxxxxxxxxxxxx>; > > > >sharmaajay@xxxxxxxxxxxxx; leon@xxxxxxxxxx; cai.huoqing@xxxxxxxxx; > > > >ssengar@xxxxxxxxxxxxxxxxxxx; vkuznets@xxxxxxxxxx; tglx@xxxxxxxxxxxxx; linux- > > > >hyperv@xxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; > > > >linux-rdma@xxxxxxxxxxxxxxx; Souradeep Chakrabarti > > > ><schakrabarti@xxxxxxxxxxxxx>; Paul Rosswurm <paulros@xxxxxxxxxxxxx> > > > >Subject: [EXTERNAL] Re: [PATCH V2 net-next] net: mana: Assigning IRQ affinity on > > > >HT cores > > > > > > > >On Tue, 21 Nov 2023 05:54:37 -0800 Souradeep Chakrabarti wrote: > > > >> Existing MANA design assigns IRQ to every CPUs, including sibling > > > >> hyper-threads in a core. This causes multiple IRQs to work on same CPU > > > >> and may reduce the network performance with RSS. > > > >> > > > >> Improve the performance by adhering the configuration for RSS, which > > > >> assigns IRQ on HT cores. > > > > > > > >Drivers should not have to carry 120 LoC for something as basic as spreading IRQs. > > > >Please take a look at include/linux/topology.h and if there's nothing that fits your > > > >needs there - add it. That way other drivers can reuse it. > > > Because of the current design idea, it is easier to keep things inside > > > the mana driver code here. As the idea of IRQ distribution here is : > > > 1)Loop through interrupts to assign CPU > > > 2)Find non sibling online CPU from local NUMA and assign the IRQs > > > on them. > > > 3)If number of IRQs is more than number of non-sibling CPU in that > > > NUMA node, then assign on sibling CPU of that node. > > > 4)Keep doing it till all the online CPUs are used or no more IRQs. > > > 5)If all CPUs in that node are used, goto next NUMA node with CPU. > > > Keep doing 2 and 3. > > > 6) If all CPUs in all NUMA nodes are used, but still there are IRQs > > > then wrap over from first local NUMA node and continue > > > doing 2, 3 4 till all IRQs are assigned. > > > > Hi Souradeep, > > > > (Thanks Jakub for sharing this thread with me) > > > > If I understand your intention right, you can leverage the existing > > cpumask_local_spread(). > > > > But I think I've got something better for you. The below series adds > > a for_each_numa_cpu() iterator, which may help you doing most of the > > job without messing with nodes internals. > > > > https://lore.kernel.org/netdev/ZD3l6FBnUh9vTIGc@yury-ThinkPad/T/ > > > Thanks Yur and Jakub. I was trying to find this patch, but unable to find it on that thread. > Also in net-next I am unable to find it. Can you please tell, if it has been committed? > If not can you please point me out the correct patch for this macro. It will be > really helpful. Try this branch. I just rebased it on top of bitmap-for-next, but didn't re-test. You may need to exclude the "sched: drop for_each_numa_hop_mask()" patch. https://github.com/norov/linux/commits/for_each_numa_cpu > > By using it, the pseudocode implementing your algorithm may look > > like this: > > > > unsigned int cpu, hop; > > unsigned int irq = 0; > > > > again: > > cpu = get_cpu(); > > node = cpu_to_node(cpu); > > cpumask_copy(cpus, cpu_online_mask); > > > > for_each_numa_cpu(cpu, hop, node, cpus) { > > /* All siblings are the same for IRQ spreading purpose */ > > irq_set_affinity_and_hint(irq, topology_sibling_cpumask()); > > > > /* One IRQ per sibling group */ > > cpumask_andnot(cpus, cpus, topology_sibling_cpumask()); > > > > if (++irq == num_irqs) > > break; > > } > > > > if (irq < num_irqs) > > goto again; > > > > (Completely not tested, just an idea.) > > > I have done similar kind of change for our driver, but constraint here is that total number of IRQs > can be equal to the total number of online CPUs, in some setup. It is either equal > to the number of online CPUs or maximum 64 IRQs if online CPUs are more than that. Not sure I understand you. If you're talking about my proposal, there's seemingly no constraints on number of CPUs/IRQs. > So my proposed change is following: > > +static int irq_setup(int *irqs, int nvec, int start_numa_node) > +{ > + cpumask_var_t node_cpumask; > + int i, cpu, err = 0; > + unsigned int next_node; > + cpumask_t visited_cpus; > + unsigned int start_node = start_numa_node; > + i = 0; > + if (!alloc_cpumask_var(&node_cpumask, GFP_KERNEL)) { > + err = -ENOMEM; > + goto free_mask; > + } > + cpumask_andnot(&visited_cpus, &visited_cpus, &visited_cpus); > + start_node = 1; > + for_each_next_node_with_cpus(start_node, next_node) { If your goal is to maximize locality, this doesn't seem to be correct. for_each_next_node_with_cpus() is based on next_node(), and so enumerates nodes in a numerically increasing order. On real machines, it's possible that numerically adjacent node is not the topologically nearest. To approach that, for every node kernel maintains a list of equally distant nodes grouped into hops. You may likely want to use for_each_numa_hop_mask iterator, which iterated over hops in increasing distance order, instead of NUMA node numbers. But I would like to see for_each_numa_cpu() finally merged as a simpler and nicer alternative. > + cpumask_copy(node_cpumask, cpumask_of_node(next_node)); > + for_each_cpu(cpu, node_cpumask) { > + cpumask_andnot(node_cpumask, node_cpumask, > + topology_sibling_cpumask(cpu)); > + irq_set_affinity_and_hint(irqs[i], cpumask_of(cpu)); > + if(++i == nvec) > + goto free_mask; > + cpumask_set_cpu(cpu, &visited_cpus); > + if (cpumask_empty(node_cpumask) && cpumask_weight(&visited_cpus) < > + nr_cpus_node(next_node)) { > + cpumask_copy(node_cpumask, cpumask_of_node(next_node)); > + cpumask_andnot(node_cpumask, node_cpumask, &visited_cpus); > + cpu = cpumask_first(node_cpumask); > + } > + } > + if (next_online_node(next_node) == MAX_NUMNODES) > + next_node = first_online_node; > + } > +free_mask: > + free_cpumask_var(node_cpumask); > + return err; > +} > > I can definitely use the for_each_numa_cpu() instead of my proposed for_each_next_node_with_cpus() > macro here and that will make it cleaner. > Thanks for the suggestion. Sure. Can you please share performance measurements for a solution you'll finally choose? Would be interesting to compare different approaches. Thanks, Yury
