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authorJosef Bacik <josef@toxicpanda.com>2018-12-04 12:59:02 -0500
committerJens Axboe <axboe@kernel.dk>2018-12-07 22:26:38 -0700
commit84f603246db9703aca05aad58b94a54dfbf44327 (patch)
treea2235d4f431e619f04292aea0349399ab4b8da68 /block/blk-rq-qos.c
parent7754f669ffde3919e398a9e591cd7510d6cf4e73 (diff)
block: add rq_qos_wait to rq_qos
Originally when I split out the common code from blk-wbt into rq_qos I left the wbt_wait() where it was and simply copied and modified it slightly to work for io-latency. However they are both basically the same thing, and as time has gone on wbt_wait() has ended up much smarter and kinder than it was when I copied it into io-latency, which means io-latency has lost out on these improvements. Since they are the same thing essentially except for a few minor things, create rq_qos_wait() that replicates what wbt_wait() currently does with callbacks that can be passed in for the snowflakes to do their own thing as appropriate. Signed-off-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/blk-rq-qos.c')
-rw-r--r--block/blk-rq-qos.c86
1 files changed, 86 insertions, 0 deletions
diff --git a/block/blk-rq-qos.c b/block/blk-rq-qos.c
index 80f603b76f61..e932ef9d2718 100644
--- a/block/blk-rq-qos.c
+++ b/block/blk-rq-qos.c
@@ -176,6 +176,92 @@ void rq_depth_scale_down(struct rq_depth *rqd, bool hard_throttle)
rq_depth_calc_max_depth(rqd);
}
+struct rq_qos_wait_data {
+ struct wait_queue_entry wq;
+ struct task_struct *task;
+ struct rq_wait *rqw;
+ acquire_inflight_cb_t *cb;
+ void *private_data;
+ bool got_token;
+};
+
+static int rq_qos_wake_function(struct wait_queue_entry *curr,
+ unsigned int mode, int wake_flags, void *key)
+{
+ struct rq_qos_wait_data *data = container_of(curr,
+ struct rq_qos_wait_data,
+ wq);
+
+ /*
+ * If we fail to get a budget, return -1 to interrupt the wake up loop
+ * in __wake_up_common.
+ */
+ if (!data->cb(data->rqw, data->private_data))
+ return -1;
+
+ data->got_token = true;
+ list_del_init(&curr->entry);
+ wake_up_process(data->task);
+ return 1;
+}
+
+/**
+ * rq_qos_wait - throttle on a rqw if we need to
+ * @private_data - caller provided specific data
+ * @acquire_inflight_cb - inc the rqw->inflight counter if we can
+ * @cleanup_cb - the callback to cleanup in case we race with a waker
+ *
+ * This provides a uniform place for the rq_qos users to do their throttling.
+ * Since you can end up with a lot of things sleeping at once, this manages the
+ * waking up based on the resources available. The acquire_inflight_cb should
+ * inc the rqw->inflight if we have the ability to do so, or return false if not
+ * and then we will sleep until the room becomes available.
+ *
+ * cleanup_cb is in case that we race with a waker and need to cleanup the
+ * inflight count accordingly.
+ */
+void rq_qos_wait(struct rq_wait *rqw, void *private_data,
+ acquire_inflight_cb_t *acquire_inflight_cb,
+ cleanup_cb_t *cleanup_cb)
+{
+ struct rq_qos_wait_data data = {
+ .wq = {
+ .func = rq_qos_wake_function,
+ .entry = LIST_HEAD_INIT(data.wq.entry),
+ },
+ .task = current,
+ .rqw = rqw,
+ .cb = acquire_inflight_cb,
+ .private_data = private_data,
+ };
+ bool has_sleeper;
+
+ has_sleeper = wq_has_sleeper(&rqw->wait);
+ if (!has_sleeper && acquire_inflight_cb(rqw, private_data))
+ return;
+
+ prepare_to_wait_exclusive(&rqw->wait, &data.wq, TASK_UNINTERRUPTIBLE);
+ do {
+ if (data.got_token)
+ break;
+ if (!has_sleeper && acquire_inflight_cb(rqw, private_data)) {
+ finish_wait(&rqw->wait, &data.wq);
+
+ /*
+ * We raced with wbt_wake_function() getting a token,
+ * which means we now have two. Put our local token
+ * and wake anyone else potentially waiting for one.
+ */
+ if (data.got_token)
+ cleanup_cb(rqw, private_data);
+ break;
+ }
+ io_schedule();
+ has_sleeper = false;
+ } while (1);
+ finish_wait(&rqw->wait, &data.wq);
+}
+
void rq_qos_exit(struct request_queue *q)
{
while (q->rq_qos) {