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blk-mq: respect rq_affinity 

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>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Christoph Hellwig 2014-04-25 02:32:53 -07:00 committed by Jens Axboe
parent 87ee7b1121
commit 3853520163
4 changed files with 6 additions and 46 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

42
block/blk-mq-sysfs.c
View File

@ -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,

8
block/blk-mq.c
View File

@ -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;

1
block/blk-mq.h
View File

@ -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];

1
include/linux/blk-mq.h
View File

@ -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,