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authorLinus Torvalds <torvalds@linux-foundation.org>2021-02-22 10:53:05 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2021-02-22 10:53:05 -0800
commitae42c3173ba5cbe12fab0dad330e997c4ff9f68a (patch)
tree3900a15300c74af76828a9c5fe44d7b6531932ec
parentd652ea30ba32db12fe8365182fad5ba2e7c22822 (diff)
parentf9ab49184af093f0bf6c0e6583f5b25da2c09ff5 (diff)
Merge tag 'for-5.12/block-ipi-2021-02-21' of git://git.kernel.dk/linux-block
Pull block IPI updates from Jens Axboe: "Avoid IRQ locking for the block IPI handling (Sebastian Andrzej Siewior)" * tag 'for-5.12/block-ipi-2021-02-21' of git://git.kernel.dk/linux-block: blk-mq: Use llist_head for blk_cpu_done blk-mq: Always complete remote completions requests in softirq smp: Process pending softirqs in flush_smp_call_function_from_idle()
-rw-r--r--block/blk-mq.c109
-rw-r--r--include/linux/blkdev.h2
2 files changed, 42 insertions, 69 deletions
diff --git a/block/blk-mq.c b/block/blk-mq.c
index f21d922ecfaf..d4d7c1caa439 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -41,7 +41,7 @@
#include "blk-mq-sched.h"
#include "blk-rq-qos.h"
-static DEFINE_PER_CPU(struct list_head, blk_cpu_done);
+static DEFINE_PER_CPU(struct llist_head, blk_cpu_done);
static void blk_mq_poll_stats_start(struct request_queue *q);
static void blk_mq_poll_stats_fn(struct blk_stat_callback *cb);
@@ -567,80 +567,29 @@ void blk_mq_end_request(struct request *rq, blk_status_t error)
}
EXPORT_SYMBOL(blk_mq_end_request);
-/*
- * Softirq action handler - move entries to local list and loop over them
- * while passing them to the queue registered handler.
- */
-static __latent_entropy void blk_done_softirq(struct softirq_action *h)
+static void blk_complete_reqs(struct llist_head *list)
{
- struct list_head *cpu_list, local_list;
-
- local_irq_disable();
- cpu_list = this_cpu_ptr(&blk_cpu_done);
- list_replace_init(cpu_list, &local_list);
- local_irq_enable();
-
- while (!list_empty(&local_list)) {
- struct request *rq;
+ struct llist_node *entry = llist_reverse_order(llist_del_all(list));
+ struct request *rq, *next;
- rq = list_entry(local_list.next, struct request, ipi_list);
- list_del_init(&rq->ipi_list);
+ llist_for_each_entry_safe(rq, next, entry, ipi_list)
rq->q->mq_ops->complete(rq);
- }
}
-static void blk_mq_trigger_softirq(struct request *rq)
+static __latent_entropy void blk_done_softirq(struct softirq_action *h)
{
- struct list_head *list;
- unsigned long flags;
-
- local_irq_save(flags);
- list = this_cpu_ptr(&blk_cpu_done);
- list_add_tail(&rq->ipi_list, list);
-
- /*
- * If the list only contains our just added request, signal a raise of
- * the softirq. If there are already entries there, someone already
- * raised the irq but it hasn't run yet.
- */
- if (list->next == &rq->ipi_list)
- raise_softirq_irqoff(BLOCK_SOFTIRQ);
- local_irq_restore(flags);
+ blk_complete_reqs(this_cpu_ptr(&blk_cpu_done));
}
static int blk_softirq_cpu_dead(unsigned int cpu)
{
- /*
- * If a CPU goes away, splice its entries to the current CPU
- * and trigger a run of the softirq
- */
- local_irq_disable();
- list_splice_init(&per_cpu(blk_cpu_done, cpu),
- this_cpu_ptr(&blk_cpu_done));
- raise_softirq_irqoff(BLOCK_SOFTIRQ);
- local_irq_enable();
-
+ blk_complete_reqs(&per_cpu(blk_cpu_done, cpu));
return 0;
}
-
static void __blk_mq_complete_request_remote(void *data)
{
- struct request *rq = data;
-
- /*
- * For most of single queue controllers, there is only one irq vector
- * for handling I/O completion, and the only irq's affinity is set
- * to all possible CPUs. On most of ARCHs, this affinity means the irq
- * is handled on one specific CPU.
- *
- * So complete I/O requests in softirq context in case of single queue
- * devices to avoid degrading I/O performance due to irqsoff latency.
- */
- if (rq->q->nr_hw_queues == 1)
- blk_mq_trigger_softirq(rq);
- else
- rq->q->mq_ops->complete(rq);
+ __raise_softirq_irqoff(BLOCK_SOFTIRQ);
}
static inline bool blk_mq_complete_need_ipi(struct request *rq)
@@ -669,6 +618,30 @@ static inline bool blk_mq_complete_need_ipi(struct request *rq)
return cpu_online(rq->mq_ctx->cpu);
}
+static void blk_mq_complete_send_ipi(struct request *rq)
+{
+ struct llist_head *list;
+ unsigned int cpu;
+
+ cpu = rq->mq_ctx->cpu;
+ list = &per_cpu(blk_cpu_done, cpu);
+ if (llist_add(&rq->ipi_list, list)) {
+ INIT_CSD(&rq->csd, __blk_mq_complete_request_remote, rq);
+ smp_call_function_single_async(cpu, &rq->csd);
+ }
+}
+
+static void blk_mq_raise_softirq(struct request *rq)
+{
+ struct llist_head *list;
+
+ preempt_disable();
+ list = this_cpu_ptr(&blk_cpu_done);
+ if (llist_add(&rq->ipi_list, list))
+ raise_softirq(BLOCK_SOFTIRQ);
+ preempt_enable();
+}
+
bool blk_mq_complete_request_remote(struct request *rq)
{
WRITE_ONCE(rq->state, MQ_RQ_COMPLETE);
@@ -681,15 +654,15 @@ bool blk_mq_complete_request_remote(struct request *rq)
return false;
if (blk_mq_complete_need_ipi(rq)) {
- INIT_CSD(&rq->csd, __blk_mq_complete_request_remote, rq);
- smp_call_function_single_async(rq->mq_ctx->cpu, &rq->csd);
- } else {
- if (rq->q->nr_hw_queues > 1)
- return false;
- blk_mq_trigger_softirq(rq);
+ blk_mq_complete_send_ipi(rq);
+ return true;
}
- return true;
+ if (rq->q->nr_hw_queues == 1) {
+ blk_mq_raise_softirq(rq);
+ return true;
+ }
+ return false;
}
EXPORT_SYMBOL_GPL(blk_mq_complete_request_remote);
@@ -3957,7 +3930,7 @@ static int __init blk_mq_init(void)
int i;
for_each_possible_cpu(i)
- INIT_LIST_HEAD(&per_cpu(blk_cpu_done, i));
+ init_llist_head(&per_cpu(blk_cpu_done, i));
open_softirq(BLOCK_SOFTIRQ, blk_done_softirq);
cpuhp_setup_state_nocalls(CPUHP_BLOCK_SOFTIRQ_DEAD,
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 9149f4a5adb3..69035e9f632b 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -153,7 +153,7 @@ struct request {
*/
union {
struct hlist_node hash; /* merge hash */
- struct list_head ipi_list;
+ struct llist_node ipi_list;
};
/*