Messages in this thread | | | Date | Wed, 11 Dec 2019 10:08:23 +0100 | From | Michal Hocko <> | Subject | Re: [PATCH v4] lib: optimize cpumask_local_spread() |
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On Wed 11-12-19 16:03:57, Shaokun Zhang wrote: > From: yuqi jin <jinyuqi@huawei.com> > > In multi-processor and NUMA system, I/O driver will find cpu cores that > which shall be bound IRQ. When cpu cores in the local numa have been > used, it is better to find the node closest to the local numa node for > performance, instead of choosing any online cpu immediately. > > On Huawei Kunpeng 920 server, there are 4 NUMA node(0 - 3) in the 2-cpu > system(0 - 1). The topology of this server is followed: > available: 4 nodes (0-3) > node 0 cpus: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 > node 0 size: 63379 MB > node 0 free: 61899 MB > node 1 cpus: 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 > node 1 size: 64509 MB > node 1 free: 63942 MB > node 2 cpus: 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 > node 2 size: 64509 MB > node 2 free: 63056 MB > node 3 cpus: 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 > node 3 size: 63997 MB > node 3 free: 63420 MB > node distances: > node 0 1 2 3 > 0: 10 16 32 33 > 1: 16 10 25 32 > 2: 32 25 10 16 > 3: 33 32 16 10 > > We perform PS (parameter server) business test, the behavior of the > service is that the client initiates a request through the network card, > the server responds to the request after calculation. When two PS > processes run on node2 and node3 separately and the network card is > located on 'node2' which is in cpu1, the performance of node2 (26W QPS) > and node3 (22W QPS) is different. > It is better that the NIC queues are bound to the cpu1 cores in turn, > then XPS will also be properly initialized, while cpumask_local_spread > only considers the local node. When the number of NIC queues exceeds the > number of cores in the local node, it returns to the online core directly. > So when PS runs on node3 sending a calculated request, the performance is > not as good as the node2. > The IRQ from 369-392 will be bound from NUMA node0 to NUMA node3 with this > patch, before the patch: > Euler:/sys/bus/pci # cat /proc/irq/369/smp_affinity_list > 0 > Euler:/sys/bus/pci # cat /proc/irq/370/smp_affinity_list > 1 > ... > Euler:/sys/bus/pci # cat /proc/irq/391/smp_affinity_list > 22 > Euler:/sys/bus/pci # cat /proc/irq/392/smp_affinity_list > 23 > After the patch: > Euler:/sys/bus/pci # cat /proc/irq/369/smp_affinity_list > 72 > Euler:/sys/bus/pci # cat /proc/irq/370/smp_affinity_list > 73 > ... > Euler:/sys/bus/pci # cat /proc/irq/391/smp_affinity_list > 94 > Euler:/sys/bus/pci # cat /proc/irq/392/smp_affinity_list > 95 > So the performance of the node3 is the same as node2 that is 26W QPS when > the network card is still in 'node2' with the patch. > > It is considered that the NIC and other I/O devices shall initialize the > interrupt binding, if the cores of the local node are used up, it is > reasonable to return the node closest to it. Let's optimize it and find > the nearest node through NUMA distance for the non-local NUMA nodes.
As I've said/asked earlier. I am missing some background how this is affecting other existing users. Is this just that nobody has noticed the suboptimal cpu usage or is your workload very special in that regards.
> Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Juergen Gross <jgross@suse.com> > Cc: Paul Burton <paul.burton@mips.com> > Cc: Michal Hocko <mhocko@suse.com> > Cc: Michael Ellerman <mpe@ellerman.id.au> > Cc: Mike Rapoport <rppt@linux.ibm.com> > Cc: Anshuman Khandual <anshuman.khandual@arm.com> > Signed-off-by: yuqi jin <jinyuqi@huawei.com> > Signed-off-by: Shaokun Zhang <zhangshaokun@hisilicon.com> > --- > ChangeLog from v3: > 1. Make spread_lock local to cpumask_local_spread(); > 2. Add more descriptions on the affinities change in log; > > ChangeLog from v2: > 1. Change the variables as static and use spinlock to protect; > 2. Give more explantation on test and performance; > > lib/cpumask.c | 102 +++++++++++++++++++++++++++++++++++++++++++++++++++------- > 1 file changed, 90 insertions(+), 12 deletions(-) > > diff --git a/lib/cpumask.c b/lib/cpumask.c > index 0cb672eb107c..f7394ba36116 100644 > --- a/lib/cpumask.c > +++ b/lib/cpumask.c > @@ -6,6 +6,7 @@ > #include <linux/export.h> > #include <linux/memblock.h> > #include <linux/numa.h> > +#include <linux/spinlock.h> > > /** > * cpumask_next - get the next cpu in a cpumask > @@ -192,18 +193,39 @@ void __init free_bootmem_cpumask_var(cpumask_var_t mask) > } > #endif > > -/** > - * cpumask_local_spread - select the i'th cpu with local numa cpu's first > - * @i: index number > - * @node: local numa_node > - * > - * This function selects an online CPU according to a numa aware policy; > - * local cpus are returned first, followed by non-local ones, then it > - * wraps around. > - * > - * It's not very efficient, but useful for setup. > - */ > -unsigned int cpumask_local_spread(unsigned int i, int node) > +static void calc_node_distance(int *node_dist, int node) > +{ > + int i; > + > + for (i = 0; i < nr_node_ids; i++) > + node_dist[i] = node_distance(node, i); > +} > + > +static int find_nearest_node(int *node_dist, bool *used) > +{ > + int i, min_dist = node_dist[0], node_id = -1; > + > + /* Choose the first unused node to compare */ > + for (i = 0; i < nr_node_ids; i++) { > + if (used[i] == 0) { > + min_dist = node_dist[i]; > + node_id = i; > + break; > + } > + } > + > + /* Compare and return the nearest node */ > + for (i = 0; i < nr_node_ids; i++) { > + if (node_dist[i] < min_dist && used[i] == 0) { > + min_dist = node_dist[i]; > + node_id = i; > + } > + } > + > + return node_id; > +} > + > +static unsigned int __cpumask_local_spread(unsigned int i, int node) > { > int cpu; > > @@ -231,4 +253,60 @@ unsigned int cpumask_local_spread(unsigned int i, int node) > } > BUG(); > } > + > +/** > + * cpumask_local_spread - select the i'th cpu with local numa cpu's first > + * @i: index number > + * @node: local numa_node > + * > + * This function selects an online CPU according to a numa aware policy; > + * local cpus are returned first, followed by the nearest non-local ones, > + * then it wraps around. > + * > + * It's not very efficient, but useful for setup. > + */ > +unsigned int cpumask_local_spread(unsigned int i, int node) > +{ > + static DEFINE_SPINLOCK(spread_lock); > + static int node_dist[MAX_NUMNODES]; > + static bool used[MAX_NUMNODES]; > + unsigned long flags; > + int cpu, j, id; > + > + /* Wrap: we always want a cpu. */ > + i %= num_online_cpus(); > + > + if (node == NUMA_NO_NODE) { > + for_each_cpu(cpu, cpu_online_mask) > + if (i-- == 0) > + return cpu; > + } else { > + if (nr_node_ids > MAX_NUMNODES) > + return __cpumask_local_spread(i, node); > + > + spin_lock_irqsave(&spread_lock, flags); > + memset(used, 0, nr_node_ids * sizeof(bool)); > + calc_node_distance(node_dist, node); > + for (j = 0; j < nr_node_ids; j++) { > + id = find_nearest_node(node_dist, used); > + if (id < 0) > + break; > + > + for_each_cpu_and(cpu, cpumask_of_node(id), > + cpu_online_mask) > + if (i-- == 0) { > + spin_unlock_irqrestore(&spread_lock, > + flags); > + return cpu; > + } > + used[id] = 1; > + } > + spin_unlock_irqrestore(&spread_lock, flags); > + > + for_each_cpu(cpu, cpu_online_mask) > + if (i-- == 0) > + return cpu; > + } > + BUG(); > +} > EXPORT_SYMBOL(cpumask_local_spread); > -- > 2.7.4
-- Michal Hocko SUSE Labs
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