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blk-mq: add basic round-robin of what CPU to queue workqueue work on

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Right now we just pick the first CPU in the mask, but that can
easily overload that one. Add some basic batching and round-robin
all the entries in the mask instead.

Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Jens Axboe 2014-05-07 10:26:44 -06:00
parent 5cf8c22775
commit 506e931f92
2 changed files with 35 additions and 14 deletions
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45
block/blk-mq.c
View File

@ -670,6 +670,30 @@ static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx)
}
}
/*
* It'd be great if the workqueue API had a way to pass
* in a mask and had some smarts for more clever placement.
* For now we just round-robin here, switching for every
* BLK_MQ_CPU_WORK_BATCH queued items.
*/
static int blk_mq_hctx_next_cpu(struct blk_mq_hw_ctx *hctx)
{
int cpu = hctx->next_cpu;
if (--hctx->next_cpu_batch <= 0) {
int next_cpu;
next_cpu = cpumask_next(hctx->next_cpu, hctx->cpumask);
if (next_cpu >= nr_cpu_ids)
next_cpu = cpumask_first(hctx->cpumask);
hctx->next_cpu = next_cpu;
hctx->next_cpu_batch = BLK_MQ_CPU_WORK_BATCH;
}
return cpu;
}
void blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async)
{
if (unlikely(test_bit(BLK_MQ_S_STOPPED, &hctx->state)))
@ -682,13 +706,7 @@ void blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async)
else {
unsigned int cpu;
/*
* It'd be great if the workqueue API had a way to pass
* in a mask and had some smarts for more clever placement
* than the first CPU. Or we could round-robin here. For now,
* just queue on the first CPU.
*/
cpu = cpumask_first(hctx->cpumask);
cpu = blk_mq_hctx_next_cpu(hctx);
kblockd_schedule_delayed_work_on(cpu, &hctx->run_work, 0);
}
}
@ -795,13 +813,7 @@ void blk_mq_delay_queue(struct blk_mq_hw_ctx *hctx, unsigned long msecs)
else {
unsigned int cpu;
/*
* It'd be great if the workqueue API had a way to pass
* in a mask and had some smarts for more clever placement
* than the first CPU. Or we could round-robin here. For now,
* just queue on the first CPU.
*/
cpu = cpumask_first(hctx->cpumask);
cpu = blk_mq_hctx_next_cpu(hctx);
kblockd_schedule_delayed_work_on(cpu, &hctx->delay_work, tmo);
}
}
@ -1378,6 +1390,11 @@ static void blk_mq_map_swqueue(struct request_queue *q)
ctx->index_hw = hctx->nr_ctx;
hctx->ctxs[hctx->nr_ctx++] = ctx;
}
queue_for_each_hw_ctx(q, hctx, i) {
hctx->next_cpu = cpumask_first(hctx->cpumask);
hctx->next_cpu_batch = BLK_MQ_CPU_WORK_BATCH;
}
}
struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *set)

4
include/linux/blk-mq.h
View File

@ -21,6 +21,8 @@ struct blk_mq_hw_ctx {
struct delayed_work run_work;
struct delayed_work delay_work;
cpumask_var_t cpumask;
int next_cpu;
int next_cpu_batch;
unsigned long flags; /* BLK_MQ_F_* flags */
@ -126,6 +128,8 @@ enum {
BLK_MQ_S_STOPPED = 0,
BLK_MQ_MAX_DEPTH = 2048,
BLK_MQ_CPU_WORK_BATCH = 8,
};
struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *);