From 476f8c98a9bccccbb97866974ffc80879adf2bbb Mon Sep 17 00:00:00 2001 From: Ming Lei Date: Sun, 8 Apr 2018 17:48:09 +0800 Subject: blk-mq: avoid to write intermediate result to hctx->next_cpu This patch figures out the final selected CPU, then writes it to hctx->next_cpu once, then we can avoid to intermediate next cpu observed from other dispatch paths. Cc: Stefan Haberland Tested-by: Christian Borntraeger Reviewed-by: Christoph Hellwig Reviewed-by: Sagi Grimberg Signed-off-by: Ming Lei Signed-off-by: Jens Axboe --- block/blk-mq.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index f489ec920807..db178c577068 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1344,26 +1344,24 @@ static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx) static int blk_mq_hctx_next_cpu(struct blk_mq_hw_ctx *hctx) { bool tried = false; + int next_cpu = hctx->next_cpu; if (hctx->queue->nr_hw_queues == 1) return WORK_CPU_UNBOUND; if (--hctx->next_cpu_batch <= 0) { - int next_cpu; select_cpu: - next_cpu = cpumask_next_and(hctx->next_cpu, hctx->cpumask, + next_cpu = cpumask_next_and(next_cpu, hctx->cpumask, cpu_online_mask); if (next_cpu >= nr_cpu_ids) - next_cpu = cpumask_first_and(hctx->cpumask,cpu_online_mask); + next_cpu = cpumask_first_and(hctx->cpumask, cpu_online_mask); /* * No online CPU is found, so have to make sure hctx->next_cpu * is set correctly for not breaking workqueue. */ if (next_cpu >= nr_cpu_ids) - hctx->next_cpu = cpumask_first(hctx->cpumask); - else - hctx->next_cpu = next_cpu; + next_cpu = cpumask_first(hctx->cpumask); hctx->next_cpu_batch = BLK_MQ_CPU_WORK_BATCH; } @@ -1371,7 +1369,7 @@ select_cpu: * Do unbound schedule if we can't find a online CPU for this hctx, * and it should only happen in the path of handling CPU DEAD. */ - if (!cpu_online(hctx->next_cpu)) { + if (!cpu_online(next_cpu)) { if (!tried) { tried = true; goto select_cpu; @@ -1381,10 +1379,13 @@ select_cpu: * Make sure to re-select CPU next time once after CPUs * in hctx->cpumask become online again. */ + hctx->next_cpu = next_cpu; hctx->next_cpu_batch = 1; return WORK_CPU_UNBOUND; } - return hctx->next_cpu; + + hctx->next_cpu = next_cpu; + return next_cpu; } static void __blk_mq_delay_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async, -- cgit v1.2.3