Add support for min-timeout waits

This adds io_uring_submit_and_wait_min_timeout(), which is like
io_uring_submit_and_wait_timeout() except it adds support for a minimum
batch timeout as well.

Also adds a test case.

Commit message to be expanded...

Signed-off-by: Jens Axboe <[email protected]>

src/include/liburing.h

@@ -191,6 +191,12 @@ int io_uring_submit_and_wait_timeout(struct io_uring *ring,
 				     unsigned wait_nr,
 				     struct __kernel_timespec *ts,
 				     sigset_t *sigmask);
+int io_uring_submit_and_wait_min_timeout(struct io_uring *ring,
+					 struct io_uring_cqe **cqe_ptr,
+					 unsigned wait_nr,
+					 struct __kernel_timespec *ts,
+					 unsigned min_wait,
+					 sigset_t *sigmask);
 
 int io_uring_register_buffers(struct io_uring *ring, const struct iovec *iovecs,
 			      unsigned nr_iovecs);

src/include/liburing/io_uring.h

@@ -710,7 +710,7 @@ enum {
 struct io_uring_getevents_arg {
 	__u64	sigmask;
 	__u32	sigmask_sz;
-	__u32	pad;
+	__u32	min_wait_usec;
 	__u64	ts;
 };
 

src/liburing.map

@@ -85,3 +85,8 @@ LIBURING_2.5 {
 	global:
 		io_uring_queue_init_mem;
 } LIBURING_2.4;
+
+LIBURING_2.6 {
+	global:
+		io_uring_submit_and_wait_min_timeout;
+} LIBURING_2.5;

src/queue.c

@@ -314,11 +314,10 @@ int io_uring_wait_cqes(struct io_uring *ring, struct io_uring_cqe **cqe_ptr,
 	return __io_uring_get_cqe(ring, cqe_ptr, to_submit, wait_nr, sigmask);
 }
 
-int io_uring_submit_and_wait_timeout(struct io_uring *ring,
-				     struct io_uring_cqe **cqe_ptr,
-				     unsigned wait_nr,
-				     struct __kernel_timespec *ts,
-				     sigset_t *sigmask)
+static int __io_uring_submit_and_wait_timeout(struct io_uring *ring,
+			struct io_uring_cqe **cqe_ptr, unsigned wait_nr,
+			struct __kernel_timespec *ts,
+			unsigned int min_wait, sigset_t *sigmask)
 {
 	int to_submit;
 
@@ -327,6 +326,7 @@ int io_uring_submit_and_wait_timeout(struct io_uring *ring,
 			struct io_uring_getevents_arg arg = {
 				.sigmask	= (unsigned long) sigmask,
 				.sigmask_sz	= _NSIG / 8,
+				.min_wait_usec	= min_wait,
 				.ts		= (unsigned long) ts
 			};
 			struct get_data data = {
@@ -349,6 +349,27 @@ int io_uring_submit_and_wait_timeout(struct io_uring *ring,
 	return __io_uring_get_cqe(ring, cqe_ptr, to_submit, wait_nr, sigmask);
 }
 
+int io_uring_submit_and_wait_min_timeout(struct io_uring *ring,
+					 struct io_uring_cqe **cqe_ptr,
+					 unsigned wait_nr,
+					 struct __kernel_timespec *ts,
+					 unsigned min_wait,
+					 sigset_t *sigmask)
+{
+	return __io_uring_submit_and_wait_timeout(ring, cqe_ptr, wait_nr, ts,
+						  min_wait, sigmask);
+}
+
+int io_uring_submit_and_wait_timeout(struct io_uring *ring,
+				     struct io_uring_cqe **cqe_ptr,
+				     unsigned wait_nr,
+				     struct __kernel_timespec *ts,
+				     sigset_t *sigmask)
+{
+	return __io_uring_submit_and_wait_timeout(ring, cqe_ptr, wait_nr, ts, 0,
+						  sigmask);
+}
+
 /*
  * See io_uring_wait_cqes() - this function is the same, it just always uses
  * '1' as the wait_nr.

test/Makefile

@@ -113,6 +113,7 @@ test_srcs := \
 	link_drain.c \
 	link-timeout.c \
 	madvise.c \
+	min-timeout.c \
 	mkdir.c \
 	msg-ring.c \
 	msg-ring-flags.c \

test/min-timeout.c

@@ -0,0 +1,223 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * Description: test min timeout handling
+ *
+ */
+#include <errno.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+#include <fcntl.h>
+#include <sys/resource.h>
+#include <pthread.h>
+
+#include "liburing.h"
+#include "helpers.h"
+
+#define NPIPES	8
+#define NWRITES	6
+
+#define WAIT_USEC	(250000)
+
+struct d {
+	int fd[NPIPES];
+	long delay;
+};
+
+static void *thread_fn(void *data)
+{
+	struct d *d = data;
+	char buf[32];
+	int i;
+
+	memset(buf, 0x55, sizeof(buf));
+
+	for (i = 0; i < NWRITES; i++) {
+		int ret;
+
+		usleep(d->delay);
+		ret = write(d->fd[i], buf, sizeof(buf));
+		if (ret != sizeof(buf)) {
+			fprintf(stderr, "bad write %d\n", ret);
+			break;
+		}
+	}
+	return NULL;
+}
+
+/*
+ * Allow 25% tolerance
+ */
+static int within_range(unsigned int target, unsigned int msec)
+{
+	unsigned int high, low;
+
+	low = (target * 3) / 4;
+	high = (target * 5) / 4;
+	return (msec >= low && msec <= high);
+}
+
+static unsigned long long mtime_since(const struct timeval *s,
+				      const struct timeval *e)
+{
+	long long sec, usec;
+
+	sec = e->tv_sec - s->tv_sec;
+	usec = (e->tv_usec - s->tv_usec);
+	if (sec > 0 && usec < 0) {
+		sec--;
+		usec += 1000000;
+	}
+
+	sec *= 1000;
+	usec /= 1000;
+	return sec + usec;
+}
+
+static unsigned long long mtime_since_now(struct timeval *tv)
+{
+	struct timeval end;
+
+	gettimeofday(&end, NULL);
+	return mtime_since(tv, &end);
+}
+
+static int test(int flags, int expected_ctx, int min_wait, int write_delay,
+		int nr_cqes, int msec_target)
+{
+	struct io_uring_cqe *cqe;
+	struct io_uring_sqe *sqe;
+	struct io_uring ring;
+	struct __kernel_timespec ts;
+	struct rusage s, e;
+	pthread_t thread;
+	struct d d;
+	int ret, fds[NPIPES][2], i;
+	struct timeval start_time;
+	char buf[32];
+	void *tret;
+	long ttime;
+
+	ret = io_uring_queue_init(NPIPES, &ring, flags);
+	if (ret == -EINVAL)
+		return T_EXIT_SKIP;
+
+	for (i = 0; i < NPIPES; i++) {
+		if (pipe(fds[i]) < 0) {
+			perror("pipe");
+			return 1;
+		}
+		d.fd[i] = fds[i][1];
+	}
+
+	d.delay = write_delay;
+	pthread_create(&thread, NULL, thread_fn, &d);
+
+	for (i = 0; i < NPIPES; i++) {
+		sqe = io_uring_get_sqe(&ring);
+		io_uring_prep_read(sqe, fds[i][0], buf, sizeof(buf), 0);
+	}
+
+	ts.tv_sec = 0;
+	ts.tv_nsec = WAIT_USEC * 1000LL;
+
+	gettimeofday(&start_time, NULL);
+	getrusage(RUSAGE_THREAD, &s);
+	ret = io_uring_submit_and_wait_min_timeout(&ring, &cqe, 8, &ts, min_wait, NULL);
+	if (ret != NPIPES)
+		fprintf(stderr, "submit_and_wait=%d\n", ret);
+
+	getrusage(RUSAGE_THREAD, &e);
+	e.ru_nvcsw -= s.ru_nvcsw;
+	ttime = mtime_since_now(&start_time);
+	if (!within_range(msec_target, ttime)) {
+		fprintf(stderr, "Expected %d msec, got %ld msec\n", msec_target,
+								ttime);
+		fprintf(stderr, "flags=%x, min_wait=%d, write_delay=%d\n",
+				flags, min_wait, write_delay);
+	}
+	/* will usually be accurate, but allow for offset of 1 */
+	if (e.ru_nvcsw != expected_ctx &&
+	    (e.ru_nvcsw - expected_ctx > 1))
+		fprintf(stderr, "%ld ctx switches, expected %d\n", e.ru_nvcsw,
+								expected_ctx);
+
+	for (i = 0; i < NPIPES; i++) {
+		ret = io_uring_peek_cqe(&ring, &cqe);
+		if (ret)
+			break;
+		io_uring_cqe_seen(&ring, cqe);
+	}
+
+	if (i != nr_cqes)
+		fprintf(stderr, "Got %d CQEs, expected %d\n", i, nr_cqes);
+
+	pthread_join(thread, &tret);
+
+	for (i = 0; i < NPIPES; i++) {
+		close(fds[i][0]);
+		close(fds[i][1]);
+	}
+
+	return T_EXIT_PASS;
+}
+
+int main(int argc, char *argv[])
+{
+	int ret;
+
+	if (argc > 1)
+		return T_EXIT_SKIP;
+
+	ret = test(0, NWRITES + 1, 0, 2000, NWRITES, WAIT_USEC / 1000);
+	if (ret == T_EXIT_FAIL)
+		return T_EXIT_FAIL;
+
+	ret = test(0, NWRITES + 1, 50000, 2000, NWRITES, 50);
+	if (ret == T_EXIT_FAIL)
+		return T_EXIT_FAIL;
+
+	ret = test(0, NWRITES + 1, 500000, 2000, NWRITES, 500);
+	if (ret == T_EXIT_FAIL)
+		return T_EXIT_FAIL;
+
+	/* no writes within min timeout, but it's given. expect 1 cqe */
+	ret = test(0, 1, 10000, 20000, 1, 20);
+	if (ret == T_EXIT_FAIL)
+		return T_EXIT_FAIL;
+
+	/* same as above, but no min timeout. should time out and we get 6 */
+	ret = test(0, NWRITES + 1, 0, 20000, NWRITES, WAIT_USEC / 1000);
+	if (ret == T_EXIT_FAIL)
+		return T_EXIT_FAIL;
+
+	ret = test(IORING_SETUP_SINGLE_ISSUER | IORING_SETUP_DEFER_TASKRUN, 1,
+			0, 2000, NWRITES, WAIT_USEC / 1000);
+	if (ret == T_EXIT_FAIL)
+		return T_EXIT_FAIL;
+
+	ret = test(IORING_SETUP_SINGLE_ISSUER | IORING_SETUP_DEFER_TASKRUN, 1,
+			50000, 2000, NWRITES, 50);
+	if (ret == T_EXIT_FAIL)
+		return T_EXIT_FAIL;
+
+	ret = test(IORING_SETUP_SINGLE_ISSUER | IORING_SETUP_DEFER_TASKRUN, 1,
+			500000, 2000, NWRITES, 500);
+	if (ret == T_EXIT_FAIL)
+		return T_EXIT_FAIL;
+
+	/* no writes within min timeout, but it's given. expect 1 cqe */
+	ret = test(IORING_SETUP_SINGLE_ISSUER | IORING_SETUP_DEFER_TASKRUN, 1,
+			10000, 20000, 1, 20);
+	if (ret == T_EXIT_FAIL)
+		return T_EXIT_FAIL;
+
+	/* same as above, but no min timeout. should time out and we get 6 */
+	ret = test(IORING_SETUP_SINGLE_ISSUER | IORING_SETUP_DEFER_TASKRUN, 1,
+			0, 20000, NWRITES, WAIT_USEC / 1000);
+	if (ret == T_EXIT_FAIL)
+		return T_EXIT_FAIL;
+
+	return ret;
+}