diff options
| author | Jens Axboe <axboe@kernel.dk> | 2018-11-30 01:36:41 +0100 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2018-11-30 22:48:04 +0100 |
| commit | 5d2ee7122c73be6a3b6bfe90d237e8aed737cfaa (patch) | |
| tree | ada2bd06a0523a6ab8a9eae652034e2b0cb7b996 /drivers/target | |
| parent | sbitmap: ammortize cost of clearing bits (diff) | |
| download | linux-5d2ee7122c73be6a3b6bfe90d237e8aed737cfaa.tar.xz linux-5d2ee7122c73be6a3b6bfe90d237e8aed737cfaa.zip | |
sbitmap: optimize wakeup check
Even if we have no waiters on any of the sbitmap_queue wait states, we
still have to loop every entry to check. We do this for every IO, so
the cost adds up.
Shift a bit of the cost to the slow path, when we actually have waiters.
Wrap prepare_to_wait_exclusive() and finish_wait(), so we can maintain
an internal count of how many are currently active. Then we can simply
check this count in sbq_wake_ptr() and not have to loop if we don't
have any sleepers.
Convert the two users of sbitmap with waiting, blk-mq-tag and iSCSI.
Reviewed-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'drivers/target')
| -rw-r--r-- | drivers/target/iscsi/iscsi_target_util.c | 12 |
1 files changed, 7 insertions, 5 deletions
diff --git a/drivers/target/iscsi/iscsi_target_util.c b/drivers/target/iscsi/iscsi_target_util.c index 36b742932c72..86987da86dd6 100644 --- a/drivers/target/iscsi/iscsi_target_util.c +++ b/drivers/target/iscsi/iscsi_target_util.c @@ -150,24 +150,26 @@ void iscsit_free_r2ts_from_list(struct iscsi_cmd *cmd) static int iscsit_wait_for_tag(struct se_session *se_sess, int state, int *cpup) { int tag = -1; - DEFINE_WAIT(wait); + DEFINE_SBQ_WAIT(wait); struct sbq_wait_state *ws; + struct sbitmap_queue *sbq; if (state == TASK_RUNNING) return tag; - ws = &se_sess->sess_tag_pool.ws[0]; + sbq = &se_sess->sess_tag_pool; + ws = &sbq->ws[0]; for (;;) { - prepare_to_wait_exclusive(&ws->wait, &wait, state); + sbitmap_prepare_to_wait(sbq, ws, &wait, state); if (signal_pending_state(state, current)) break; - tag = sbitmap_queue_get(&se_sess->sess_tag_pool, cpup); + tag = sbitmap_queue_get(sbq, cpup); if (tag >= 0) break; schedule(); } - finish_wait(&ws->wait, &wait); + sbitmap_finish_wait(sbq, ws, &wait); return tag; } |