* [PATCH] blk-mq: respect rq_affinity
[not found] ` <20140425071659.GA15384@infradead.org>
@ 2014-04-25 9:32 ` Christoph Hellwig
2014-04-25 14:23 ` Jens Axboe
0 siblings, 1 reply; 2+ messages in thread
From: Christoph Hellwig @ 2014-04-25 9:32 UTC (permalink / raw)
To: Jens Axboe
Cc: Elliott, Robert (Server Storage), scameron@beardog.cce.hp.com,
Bart Van Assche, linux-kernel
From: Christoph Hellwig <hch@lst.de>
The blk-mq code is using it's own version of the I/O completion affinity
tunables, which causes a few issues:
- the rq_affinity sysfs file doesn't work for blk-mq devices, even if it
still is present, thus breaking existing tuning setups.
- the rq_affinity = 1 mode, which is the defauly for legacy request based
drivers isn't implemented at all.
- blk-mq drivers don't implement any completion affinity with the default
flag settings.
This patches removes the blk-mq ipi_redirect flag and sysfs file, as well
as the internal BLK_MQ_F_SHOULD_IPI flag and replaces it with code that
respects the queue-wide rq_affinity flags and also implements the
rq_affinity = 1 mode.
This means I/O completion affinity can now only be tuned block-queue wide
instead of per context, which seems more sensible to me anyway.
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
block/blk-mq-sysfs.c | 42 ------------------------------------------
block/blk-mq.c | 8 ++++++--
block/blk-mq.h | 1 -
include/linux/blk-mq.h | 1 -
4 files changed, 6 insertions(+), 46 deletions(-)
diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c
index 9176a69..8145b5b 100644
--- a/block/blk-mq-sysfs.c
+++ b/block/blk-mq-sysfs.c
@@ -203,42 +203,6 @@ static ssize_t blk_mq_hw_sysfs_rq_list_show(struct blk_mq_hw_ctx *hctx,
return ret;
}
-static ssize_t blk_mq_hw_sysfs_ipi_show(struct blk_mq_hw_ctx *hctx, char *page)
-{
- ssize_t ret;
-
- spin_lock(&hctx->lock);
- ret = sprintf(page, "%u\n", !!(hctx->flags & BLK_MQ_F_SHOULD_IPI));
- spin_unlock(&hctx->lock);
-
- return ret;
-}
-
-static ssize_t blk_mq_hw_sysfs_ipi_store(struct blk_mq_hw_ctx *hctx,
- const char *page, size_t len)
-{
- struct blk_mq_ctx *ctx;
- unsigned long ret;
- unsigned int i;
-
- if (kstrtoul(page, 10, &ret)) {
- pr_err("blk-mq-sysfs: invalid input '%s'\n", page);
- return -EINVAL;
- }
-
- spin_lock(&hctx->lock);
- if (ret)
- hctx->flags |= BLK_MQ_F_SHOULD_IPI;
- else
- hctx->flags &= ~BLK_MQ_F_SHOULD_IPI;
- spin_unlock(&hctx->lock);
-
- hctx_for_each_ctx(hctx, ctx, i)
- ctx->ipi_redirect = !!ret;
-
- return len;
-}
-
static ssize_t blk_mq_hw_sysfs_tags_show(struct blk_mq_hw_ctx *hctx, char *page)
{
return blk_mq_tag_sysfs_show(hctx->tags, page);
@@ -307,11 +271,6 @@ static struct blk_mq_hw_ctx_sysfs_entry blk_mq_hw_sysfs_pending = {
.attr = {.name = "pending", .mode = S_IRUGO },
.show = blk_mq_hw_sysfs_rq_list_show,
};
-static struct blk_mq_hw_ctx_sysfs_entry blk_mq_hw_sysfs_ipi = {
- .attr = {.name = "ipi_redirect", .mode = S_IRUGO | S_IWUSR},
- .show = blk_mq_hw_sysfs_ipi_show,
- .store = blk_mq_hw_sysfs_ipi_store,
-};
static struct blk_mq_hw_ctx_sysfs_entry blk_mq_hw_sysfs_tags = {
.attr = {.name = "tags", .mode = S_IRUGO },
.show = blk_mq_hw_sysfs_tags_show,
@@ -326,7 +285,6 @@ static struct attribute *default_hw_ctx_attrs[] = {
&blk_mq_hw_sysfs_run.attr,
&blk_mq_hw_sysfs_dispatched.attr,
&blk_mq_hw_sysfs_pending.attr,
- &blk_mq_hw_sysfs_ipi.attr,
&blk_mq_hw_sysfs_tags.attr,
&blk_mq_hw_sysfs_cpus.attr,
NULL,
diff --git a/block/blk-mq.c b/block/blk-mq.c
index af358b6..7c92d7d 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -326,15 +326,19 @@ static void __blk_mq_complete_request_remote(void *data)
void __blk_mq_complete_request(struct request *rq)
{
struct blk_mq_ctx *ctx = rq->mq_ctx;
+ bool shared = false;
int cpu;
- if (!ctx->ipi_redirect) {
+ if (!test_bit(QUEUE_FLAG_SAME_COMP, &rq->q->queue_flags)) {
rq->q->softirq_done_fn(rq);
return;
}
cpu = get_cpu();
- if (cpu != ctx->cpu && cpu_online(ctx->cpu)) {
+ if (!test_bit(QUEUE_FLAG_SAME_FORCE, &rq->q->queue_flags))
+ shared = cpus_share_cache(cpu, ctx->cpu);
+
+ if (cpu != ctx->cpu && !shared && cpu_online(ctx->cpu)) {
rq->csd.func = __blk_mq_complete_request_remote;
rq->csd.info = rq;
rq->csd.flags = 0;
diff --git a/block/blk-mq.h b/block/blk-mq.h
index b41a784..1ae364c 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -11,7 +11,6 @@ struct blk_mq_ctx {
unsigned int cpu;
unsigned int index_hw;
- unsigned int ipi_redirect;
/* incremented at dispatch time */
unsigned long rq_dispatched[2];
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index ab469d5..3b561d6 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -122,7 +122,6 @@ enum {
BLK_MQ_F_SHOULD_MERGE = 1 << 0,
BLK_MQ_F_SHOULD_SORT = 1 << 1,
- BLK_MQ_F_SHOULD_IPI = 1 << 2,
BLK_MQ_S_STOPPED = 0,
--
1.7.10.4
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