On 03/08/2016 10:34 AM, Jon Derrick wrote:
Extends iostats to encompass polling statistics to save a few cycles
when disabled.
Signed-off-by: Jon Derrick <jonathan.derrick@xxxxxxxxx>
---
block/blk-core.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/block/blk-core.c b/block/blk-core.c
index ab51685..354d03b 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -3350,13 +3350,16 @@ bool blk_poll(struct request_queue *q, blk_qc_t cookie)
while (!need_resched()) {
unsigned int queue_num = blk_qc_t_to_queue_num(cookie);
struct blk_mq_hw_ctx *hctx = q->queue_hw_ctx[queue_num];
+ int io_stat = blk_queue_io_stat(q);
int ret;
- hctx->poll_invoked++;
+ if (io_stat)
+ hctx->poll_invoked++;
ret = q->mq_ops->poll(hctx, blk_qc_t_to_tag(cookie));
if (ret > 0) {
- hctx->poll_success++;
+ if (io_stat)
+ hctx->poll_success++;
set_current_state(TASK_RUNNING);
return true;
}
Not sure this is a great idea. First of all, the poll stats are per
hardware queue. How many submission queues and CPUs do you have in your
setup? For most cases, I'd assume there'd be a 1:1 mapping between the
two, which makes the stats essentially free. And secondly, even for a
less optimal mapping, the poll stats are a lot cheaper than the io
stats. So bundling them together might not make a ton of sense.
--
Jens Axboe
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