| Message ID | 20201006194125.2493508-1-krisman@collabora.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v3] block: Consider only dispatched requests for inflight statistic | expand |
On 10/6/20 1:41 PM, Gabriel Krisman Bertazi wrote: > According to Documentation/block/stat.rst, inflight should not include > I/O requests that are in the queue but not yet dispatched to the device, > but blk-mq identifies as inflight any request that has a tag allocated, > which, for queues without elevator, happens at request allocation time > and before it is queued in the ctx (default case in blk_mq_submit_bio). > > In addition, current behavior is different for queues with elevator from > queues without it, since for the former the driver tag is allocated at > dispatch time. A more precise approach would be to only consider > requests with state MQ_RQ_IN_FLIGHT. > > This effectively reverts commit 6131837b1de6 ("blk-mq: count allocated > but not started requests in iostats inflight") to consolidate blk-mq > behavior with itself (elevator case) and with original documentation, > but it differs from the behavior used by the legacy path. > > This version differs from v1 by using blk_mq_rq_state to access the > state attribute. Avoid using blk_mq_request_started, which was > suggested, since we don't want to include MQ_RQ_COMPLETE. Applied, thanks.
diff --git a/block/blk-mq.c b/block/blk-mq.c index 2e4b3cad2a61..c5fefd39d0c0 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -105,7 +105,7 @@ static bool blk_mq_check_inflight(struct blk_mq_hw_ctx *hctx, { struct mq_inflight *mi = priv; - if (rq->part == mi->part) + if (rq->part == mi->part && blk_mq_rq_state(rq) == MQ_RQ_IN_FLIGHT) mi->inflight[rq_data_dir(rq)]++; return true;
According to Documentation/block/stat.rst, inflight should not include I/O requests that are in the queue but not yet dispatched to the device, but blk-mq identifies as inflight any request that has a tag allocated, which, for queues without elevator, happens at request allocation time and before it is queued in the ctx (default case in blk_mq_submit_bio). In addition, current behavior is different for queues with elevator from queues without it, since for the former the driver tag is allocated at dispatch time. A more precise approach would be to only consider requests with state MQ_RQ_IN_FLIGHT. This effectively reverts commit 6131837b1de6 ("blk-mq: count allocated but not started requests in iostats inflight") to consolidate blk-mq behavior with itself (elevator case) and with original documentation, but it differs from the behavior used by the legacy path. This version differs from v1 by using blk_mq_rq_state to access the state attribute. Avoid using blk_mq_request_started, which was suggested, since we don't want to include MQ_RQ_COMPLETE. Cc: Omar Sandoval <osandov@fb.com> Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com> --- block/blk-mq.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)