From 6a6dcae8f486c3f3298d0767d34505121c7b0b81 Mon Sep 17 00:00:00 2001 From: Ming Lei Date: Tue, 27 Dec 2022 10:29:05 +0800 Subject: blk-mq: Build default queue map via group_cpus_evenly() The default queue mapping builder of blk_mq_map_queues doesn't take NUMA topo into account, so the built mapping is pretty bad, since CPUs belonging to different NUMA node are assigned to same queue. It is observed that IOPS drops by ~30% when running two jobs on same hctx of null_blk from two CPUs belonging to two NUMA nodes compared with from same NUMA node. Address the issue by reusing group_cpus_evenly() for building queue mapping since group_cpus_evenly() does group cpus according to CPU/NUMA locality. Also performance data becomes more stable with this given correct queue mapping is applied wrt. numa locality viewpoint, for example, on one two nodes arm64 machine with 160 cpus, node 0(cpu 0~79), node 1(cpu 80~159): 1) modprobe null_blk nr_devices=1 submit_queues=2 2) run 'fio(t/io_uring -p 0 -n 4 -r 20 /dev/nullb0)', and observe that IOPS becomes much stable on multiple tests: - unpatched: IOPS is 2.5M ~ 4.5M - patched: IOPS is 4.3M ~ 5.0M Lots of drivers may benefit from the change, such as nvme pci poll, nvme tcp, ... Signed-off-by: Ming Lei Signed-off-by: Thomas Gleixner Reviewed-by: Christoph Hellwig Reviewed-by: John Garry Reviewed-by: Jens Axboe Link: https://lore.kernel.org/r/20221227022905.352674-7-ming.lei@redhat.com --- block/blk-mq-cpumap.c | 63 +++++++++++---------------------------------------- 1 file changed, 13 insertions(+), 50 deletions(-) (limited to 'block') diff --git a/block/blk-mq-cpumap.c b/block/blk-mq-cpumap.c index 9c2fce1a7b50..0c612c19feb8 100644 --- a/block/blk-mq-cpumap.c +++ b/block/blk-mq-cpumap.c @@ -10,66 +10,29 @@ #include #include #include +#include #include #include "blk.h" #include "blk-mq.h" -static int queue_index(struct blk_mq_queue_map *qmap, - unsigned int nr_queues, const int q) -{ - return qmap->queue_offset + (q % nr_queues); -} - -static int get_first_sibling(unsigned int cpu) -{ - unsigned int ret; - - ret = cpumask_first(topology_sibling_cpumask(cpu)); - if (ret < nr_cpu_ids) - return ret; - - return cpu; -} - void blk_mq_map_queues(struct blk_mq_queue_map *qmap) { - unsigned int *map = qmap->mq_map; - unsigned int nr_queues = qmap->nr_queues; - unsigned int cpu, first_sibling, q = 0; - - for_each_possible_cpu(cpu) - map[cpu] = -1; - - /* - * Spread queues among present CPUs first for minimizing - * count of dead queues which are mapped by all un-present CPUs - */ - for_each_present_cpu(cpu) { - if (q >= nr_queues) - break; - map[cpu] = queue_index(qmap, nr_queues, q++); + const struct cpumask *masks; + unsigned int queue, cpu; + + masks = group_cpus_evenly(qmap->nr_queues); + if (!masks) { + for_each_possible_cpu(cpu) + qmap->mq_map[cpu] = qmap->queue_offset; + return; } - for_each_possible_cpu(cpu) { - if (map[cpu] != -1) - continue; - /* - * First do sequential mapping between CPUs and queues. - * In case we still have CPUs to map, and we have some number of - * threads per cores then map sibling threads to the same queue - * for performance optimizations. - */ - if (q < nr_queues) { - map[cpu] = queue_index(qmap, nr_queues, q++); - } else { - first_sibling = get_first_sibling(cpu); - if (first_sibling == cpu) - map[cpu] = queue_index(qmap, nr_queues, q++); - else - map[cpu] = map[first_sibling]; - } + for (queue = 0; queue < qmap->nr_queues; queue++) { + for_each_cpu(cpu, &masks[queue]) + qmap->mq_map[cpu] = qmap->queue_offset + queue; } + kfree(masks); } EXPORT_SYMBOL_GPL(blk_mq_map_queues); -- cgit v1.2.3