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authorJens Axboe <axboe@kernel.dk>2018-11-30 03:36:41 +0300
committerJens Axboe <axboe@kernel.dk>2018-12-01 00:48:04 +0300
commit5d2ee7122c73be6a3b6bfe90d237e8aed737cfaa (patch)
treeada2bd06a0523a6ab8a9eae652034e2b0cb7b996 /drivers/target/iscsi/iscsi_target_util.c
parentea86ea2cdced20057da4d2c32965c1219c238197 (diff)
downloadlinux-5d2ee7122c73be6a3b6bfe90d237e8aed737cfaa.tar.xz
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/iscsi/iscsi_target_util.c')
-rw-r--r--drivers/target/iscsi/iscsi_target_util.c12
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;
}