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Use io_uring_sq_ready to count pending SQEs #177

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Merged
ioquatix merged 1 commit into from
May 13, 2026
Merged

Use io_uring_sq_ready to count pending SQEs #177

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31 changes: 18 additions & 13 deletions ext/io/event/selector/uring.c
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Original file line number Diff line number Diff line change
Expand Up @@ -32,7 +32,6 @@ struct IO_Event_Selector_URing
{
struct IO_Event_Selector backend;
struct io_uring ring;
size_t pending;

// Flag indicating whether the selector is currently blocked in a system call.
// Set to 1 when blocked in io_uring_wait_cqe_timeout() without GVL, 0 otherwise.
Expand Down Expand Up @@ -239,7 +238,6 @@ VALUE IO_Event_Selector_URing_allocate(VALUE self) {
IO_Event_Selector_initialize(&selector->backend, self, Qnil);
selector->ring.ring_fd = -1;

selector->pending = 0;
selector->blocked = 0;
selector->interrupt.descriptor = -1;
selector->wakeup_registered = 0;
Expand Down Expand Up @@ -421,15 +419,14 @@ void IO_Event_Selector_URing_dump_completion_queue(struct IO_Event_Selector_URin
// Flush the submission queue, optionally yielding if unsuccessful.
static
int io_uring_submit_all(struct IO_Event_Selector_URing *selector, bool yield) {
while (selector->pending > 0) {
struct io_uring *ring = &selector->ring;

while (io_uring_sq_ready(ring) > 0) {
int result = io_uring_submit(&selector->ring);

if (result >= 0) {
// io_uring_submit() returns the number of submitted SQEs
selector->pending -= result;
} else if (result == -EBUSY || result == -EAGAIN) {
if (result == -EBUSY || result == -EAGAIN) {
if (yield) IO_Event_Selector_yield(&selector->backend);
} else {
} else if (result < 0) {
rb_syserr_fail(-result, "io_uring_submit_all:io_uring_submit");
return result;
}
Expand All @@ -442,23 +439,32 @@ int io_uring_submit_all(struct IO_Event_Selector_URing *selector, bool yield) {
// Flush the submission queue if pending operations are present.
static
int io_uring_submit_flush(struct IO_Event_Selector_URing *selector) {
if (DEBUG) fprintf(stderr, "io_uring_submit_now(pending=%ld)\n", selector->pending);
if (DEBUG) {
unsigned pending = io_uring_sq_ready(&selector->ring);
fprintf(stderr, "io_uring_submit_flush(pending=%u)\n", pending);
}

return io_uring_submit_all(selector, false);
}

// Immediately flush the submission queue, yielding to the event loop if it was not successful.
static
int io_uring_submit_now(struct IO_Event_Selector_URing *selector) {
if (DEBUG) fprintf(stderr, "io_uring_submit_now(pending=%ld)\n", selector->pending);

if (DEBUG) {
unsigned pending = io_uring_sq_ready(&selector->ring);
fprintf(stderr, "io_uring_submit_now(pending=%u)\n", pending);
}

return io_uring_submit_all(selector, true);
}

// Submit a pending operation. This does not submit the operation immediately, but instead defers it to the next call to `io_uring_submit_flush` or `io_uring_submit_now`. This is useful for operations that are not urgent, but should be used with care as it can lead to a deadlock if the submission queue is not flushed.
static
void io_uring_submit_pending(struct IO_Event_Selector_URing *selector) {
if (DEBUG) fprintf(stderr, "io_uring_submit_pending(ring=%p, pending=%ld)\n", &selector->ring, selector->pending);
if (DEBUG) {
unsigned pending = io_uring_sq_ready(&selector->ring);
fprintf(stderr, "io_uring_submit_pending(ring=%p, pending=%u)\n", &selector->ring, pending);
}
}

struct io_uring_sqe * io_get_sqe(struct IO_Event_Selector_URing *selector) {
Expand All @@ -471,7 +477,6 @@ struct io_uring_sqe * io_get_sqe(struct IO_Event_Selector_URing *selector) {
sqe = io_uring_get_sqe(&selector->ring);
}

selector->pending += 1;
return sqe;
}

Expand Down
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