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block: make unplug timer trace event correspond to the schedule() unplug
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It's a pretty close match to what we had before - the timer triggering
would mean that nobody unplugged the plug in due time, in the new
scheme this matches very closely what the schedule() unplug now is.
It's essentially the difference between an explicit unplug (IO unplug)
or an implicit unplug (timer unplug, we scheduled with pending IO
queued).

Signed-off-by: Jens Axboe <[email protected]>
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Jens Axboe committed Apr 16, 2011
1 parent a237c1c commit 49cac01
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Showing 3 changed files with 31 additions and 18 deletions.
18 changes: 12 additions & 6 deletions block/blk-core.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2662,17 +2662,23 @@ static int plug_rq_cmp(void *priv, struct list_head *a, struct list_head *b)
return !(rqa->q <= rqb->q);
}

/*
* If 'from_schedule' is true, then postpone the dispatch of requests
* until a safe kblockd context. We due this to avoid accidental big
* additional stack usage in driver dispatch, in places where the originally
* plugger did not intend it.
*/
static void queue_unplugged(struct request_queue *q, unsigned int depth,
bool force_kblockd)
bool from_schedule)
{
trace_block_unplug_io(q, depth);
__blk_run_queue(q, force_kblockd);
trace_block_unplug(q, depth, !from_schedule);
__blk_run_queue(q, from_schedule);

if (q->unplugged_fn)
q->unplugged_fn(q);
}

void blk_flush_plug_list(struct blk_plug *plug, bool force_kblockd)
void blk_flush_plug_list(struct blk_plug *plug, bool from_schedule)
{
struct request_queue *q;
unsigned long flags;
Expand Down Expand Up @@ -2707,7 +2713,7 @@ void blk_flush_plug_list(struct blk_plug *plug, bool force_kblockd)
BUG_ON(!rq->q);
if (rq->q != q) {
if (q) {
queue_unplugged(q, depth, force_kblockd);
queue_unplugged(q, depth, from_schedule);
spin_unlock(q->queue_lock);
}
q = rq->q;
Expand All @@ -2728,7 +2734,7 @@ void blk_flush_plug_list(struct blk_plug *plug, bool force_kblockd)
}

if (q) {
queue_unplugged(q, depth, force_kblockd);
queue_unplugged(q, depth, from_schedule);
spin_unlock(q->queue_lock);
}

Expand Down
13 changes: 7 additions & 6 deletions include/trace/events/block.h
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Original file line number Diff line number Diff line change
Expand Up @@ -401,9 +401,9 @@ TRACE_EVENT(block_plug,

DECLARE_EVENT_CLASS(block_unplug,

TP_PROTO(struct request_queue *q, unsigned int depth),
TP_PROTO(struct request_queue *q, unsigned int depth, bool explicit),

TP_ARGS(q, depth),
TP_ARGS(q, depth, explicit),

TP_STRUCT__entry(
__field( int, nr_rq )
Expand All @@ -419,18 +419,19 @@ DECLARE_EVENT_CLASS(block_unplug,
);

/**
* block_unplug_io - release of operations requests in request queue
* block_unplug - release of operations requests in request queue
* @q: request queue to unplug
* @depth: number of requests just added to the queue
* @explicit: whether this was an explicit unplug, or one from schedule()
*
* Unplug request queue @q because device driver is scheduled to work
* on elements in the request queue.
*/
DEFINE_EVENT(block_unplug, block_unplug_io,
DEFINE_EVENT(block_unplug, block_unplug,

TP_PROTO(struct request_queue *q, unsigned int depth),
TP_PROTO(struct request_queue *q, unsigned int depth, bool explicit),

TP_ARGS(q, depth)
TP_ARGS(q, depth, explicit)
);

/**
Expand Down
18 changes: 12 additions & 6 deletions kernel/trace/blktrace.c
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Original file line number Diff line number Diff line change
Expand Up @@ -850,16 +850,21 @@ static void blk_add_trace_plug(void *ignore, struct request_queue *q)
__blk_add_trace(bt, 0, 0, 0, BLK_TA_PLUG, 0, 0, NULL);
}

static void blk_add_trace_unplug_io(void *ignore, struct request_queue *q,
unsigned int depth)
static void blk_add_trace_unplug(void *ignore, struct request_queue *q,
unsigned int depth, bool explicit)
{
struct blk_trace *bt = q->blk_trace;

if (bt) {
__be64 rpdu = cpu_to_be64(depth);
u32 what;

__blk_add_trace(bt, 0, 0, 0, BLK_TA_UNPLUG_IO, 0,
sizeof(rpdu), &rpdu);
if (explicit)
what = BLK_TA_UNPLUG_IO;
else
what = BLK_TA_UNPLUG_TIMER;

__blk_add_trace(bt, 0, 0, 0, what, 0, sizeof(rpdu), &rpdu);
}
}

Expand Down Expand Up @@ -1002,7 +1007,7 @@ static void blk_register_tracepoints(void)
WARN_ON(ret);
ret = register_trace_block_plug(blk_add_trace_plug, NULL);
WARN_ON(ret);
ret = register_trace_block_unplug_io(blk_add_trace_unplug_io, NULL);
ret = register_trace_block_unplug(blk_add_trace_unplug, NULL);
WARN_ON(ret);
ret = register_trace_block_split(blk_add_trace_split, NULL);
WARN_ON(ret);
Expand All @@ -1017,7 +1022,7 @@ static void blk_unregister_tracepoints(void)
unregister_trace_block_rq_remap(blk_add_trace_rq_remap, NULL);
unregister_trace_block_bio_remap(blk_add_trace_bio_remap, NULL);
unregister_trace_block_split(blk_add_trace_split, NULL);
unregister_trace_block_unplug_io(blk_add_trace_unplug_io, NULL);
unregister_trace_block_unplug(blk_add_trace_unplug, NULL);
unregister_trace_block_plug(blk_add_trace_plug, NULL);
unregister_trace_block_sleeprq(blk_add_trace_sleeprq, NULL);
unregister_trace_block_getrq(blk_add_trace_getrq, NULL);
Expand Down Expand Up @@ -1332,6 +1337,7 @@ static const struct {
[__BLK_TA_COMPLETE] = {{ "C", "complete" }, blk_log_with_error },
[__BLK_TA_PLUG] = {{ "P", "plug" }, blk_log_plug },
[__BLK_TA_UNPLUG_IO] = {{ "U", "unplug_io" }, blk_log_unplug },
[__BLK_TA_UNPLUG_TIMER] = {{ "UT", "unplug_timer" }, blk_log_unplug },
[__BLK_TA_INSERT] = {{ "I", "insert" }, blk_log_generic },
[__BLK_TA_SPLIT] = {{ "X", "split" }, blk_log_split },
[__BLK_TA_BOUNCE] = {{ "B", "bounce" }, blk_log_generic },
Expand Down

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