sundb · sundb · Mar 22, 2026
diff --git a/src/Makefile b/src/Makefile
@@ -343,6 +343,24 @@ ifneq ($(SKIP_VEC_SETS),yes)
 	FINAL_CFLAGS+=-DINCLUDE_VEC_SETS=1
 endif
 
+# io_uring support (Linux 5.6+, requires liburing)
+LIBURING_LIBS=
+LIBURING_PKGCONFIG := $(shell $(PKG_CONFIG) --exists liburing 2>/dev/null && echo $$?)
+ifeq ($(LIBURING_PKGCONFIG),0)
+	LIBURING_LIBS=$(shell $(PKG_CONFIG) --libs liburing)
+	LIBURING_CFLAGS=$(shell $(PKG_CONFIG) --cflags liburing)
+else
+	LIBURING_LIBS=-luring
+	LIBURING_CFLAGS=
+endif
+
+ifeq ($(USE_IO_URING),yes)
+ifeq ($(uname_S),Linux)
+	FINAL_CFLAGS+= -DHAVE_IO_URING $(LIBURING_CFLAGS)
+	FINAL_LIBS+= $(LIBURING_LIBS)
+endif
+endif
+
 ifndef V
     define MAKE_INSTALL
         @printf '    %b %b\n' $(LINKCOLOR)INSTALL$(ENDCOLOR) $(BINCOLOR)$(1)$(ENDCOLOR) 1>&2
@@ -382,7 +400,7 @@ endif
 
 REDIS_SERVER_NAME=redis-server$(PROG_SUFFIX)
 REDIS_SENTINEL_NAME=redis-sentinel$(PROG_SUFFIX)
-REDIS_SERVER_OBJ=threads_mngr.o memory_prefetch.o adlist.o quicklist.o ae.o anet.o dict.o ebuckets.o eventnotifier.o iothread.o mstr.o entry.o kvstore.o fwtree.o estore.o server.o sds.o zmalloc.o lzf_c.o lzf_d.o pqsort.o zipmap.o sha1.o ziplist.o release.o networking.o util.o object.o db.o replication.o rdb.o t_string.o t_list.o t_set.o t_zset.o t_hash.o config.o aof.o pubsub.o multi.o debug.o sort.o intset.o syncio.o cluster.o cluster_asm.o cluster_legacy.o cluster_slot_stats.o crc16.o endianconv.o slowlog.o eval.o bio.o rio.o rand.o memtest.o syscheck.o crcspeed.o crccombine.o crc64.o bitops.o sentinel.o notify.o setproctitle.o blocked.o hyperloglog.o latency.o sparkline.o redis-check-rdb.o redis-check-aof.o geo.o lazyfree.o module.o evict.o expire.o geohash.o geohash_helper.o childinfo.o defrag.o siphash.o rax.o t_stream.o listpack.o localtime.o lolwut.o lolwut5.o lolwut6.o lolwut8.o acl.o tracking.o socket.o tls.o sha256.o timeout.o setcpuaffinity.o monotonic.o mt19937-64.o resp_parser.o call_reply.o script_lua.o script.o functions.o function_lua.o commands.o strl.o connection.o unix.o logreqres.o keymeta.o chk.o hotkeys.o gcra.o
+REDIS_SERVER_OBJ=threads_mngr.o memory_prefetch.o adlist.o quicklist.o ae.o anet.o dict.o ebuckets.o eventnotifier.o iothread.o mstr.o entry.o kvstore.o fwtree.o estore.o server.o sds.o zmalloc.o lzf_c.o lzf_d.o pqsort.o zipmap.o sha1.o ziplist.o release.o networking.o util.o object.o db.o replication.o rdb.o t_string.o t_list.o t_set.o t_zset.o t_hash.o config.o aof.o pubsub.o multi.o debug.o sort.o intset.o syncio.o cluster.o cluster_asm.o cluster_legacy.o cluster_slot_stats.o crc16.o endianconv.o slowlog.o eval.o bio.o rio.o rand.o memtest.o syscheck.o crcspeed.o crccombine.o crc64.o bitops.o sentinel.o notify.o setproctitle.o blocked.o hyperloglog.o latency.o sparkline.o redis-check-rdb.o redis-check-aof.o geo.o lazyfree.o module.o evict.o expire.o geohash.o geohash_helper.o childinfo.o defrag.o siphash.o rax.o t_stream.o listpack.o localtime.o lolwut.o lolwut5.o lolwut6.o lolwut8.o acl.o tracking.o socket.o tls.o sha256.o timeout.o setcpuaffinity.o monotonic.o mt19937-64.o resp_parser.o call_reply.o script_lua.o script.o functions.o function_lua.o commands.o strl.o connection.o unix.o logreqres.o keymeta.o chk.o hotkeys.o gcra.o io_uring_batch.o
 REDIS_CLI_NAME=redis-cli$(PROG_SUFFIX)
 REDIS_CLI_OBJ=anet.o adlist.o dict.o redis-cli.o zmalloc.o release.o ae.o redisassert.o crcspeed.o crccombine.o crc64.o siphash.o crc16.o monotonic.o cli_common.o mt19937-64.o strl.o cli_commands.o
 REDIS_BENCHMARK_NAME=redis-benchmark$(PROG_SUFFIX)
@@ -417,6 +435,7 @@ persist-settings: distclean
 	echo MALLOC=$(MALLOC) >> .make-settings
 	echo BUILD_TLS=$(BUILD_TLS) >> .make-settings
 	echo USE_SYSTEMD=$(USE_SYSTEMD) >> .make-settings
+	echo USE_IO_URING=$(USE_IO_URING) >> .make-settings
 	echo CFLAGS=$(CFLAGS) >> .make-settings
 	echo LDFLAGS=$(LDFLAGS) >> .make-settings
 	echo REDIS_CFLAGS=$(REDIS_CFLAGS) >> .make-settings

diff --git a/src/ae.c b/src/ae.c
@@ -29,16 +29,20 @@
 
 /* Include the best multiplexing layer supported by this system.
  * The following should be ordered by performances, descending. */
-#ifdef HAVE_EVPORT
-#include "ae_evport.c"
+#ifdef HAVE_IO_URING
+#include "ae_io_uring.c"
 #else
-    #ifdef HAVE_EPOLL
-    #include "ae_epoll.c"
+    #ifdef HAVE_EVPORT
+    #include "ae_evport.c"
     #else
-        #ifdef HAVE_KQUEUE
-        #include "ae_kqueue.c"
+        #ifdef HAVE_EPOLL
+        #include "ae_epoll.c"
         #else
-        #include "ae_select.c"
+            #ifdef HAVE_KQUEUE
+            #include "ae_kqueue.c"
+            #else
+            #include "ae_select.c"
+            #endif
         #endif
     #endif
 #endif

diff --git a/src/ae_io_uring.c b/src/ae_io_uring.c
@@ -0,0 +1,266 @@
+/* Linux io_uring based ae.c module with epoll fallback
+ *
+ * Copyright (c) 2024-Present, Redis Ltd.
+ * All rights reserved.
+ *
+ * Licensed under your choice of (a) the Redis Source Available License 2.0
+ * (RSALv2); or (b) the Server Side Public License v1 (SSPLv1); or (c) the
+ * GNU Affero General Public License v3 (AGPLv3).
+ *
+ * This module uses io_uring multishot poll for event readiness notification.
+ * Requires Linux 5.6+ and liburing. If io_uring initialization fails at
+ * runtime (old kernel, insufficient resources), falls back to epoll
+ * transparently within the same binary.
+ */
+
+#include <liburing.h>
+#include <sys/epoll.h>
+#include <poll.h>
+
+#define AE_IO_URING_RING_ENTRIES 4096
+
+#define IOURING_USERDATA(fd, mask) (((uint64_t)(unsigned)(fd)) | ((uint64_t)(mask) << 32))
+#define IOURING_USERDATA_FD(ud) ((int)((ud) & 0xFFFFFFFF))
+#define IOURING_USERDATA_MASK(ud) ((int)((ud) >> 32))
+
+#define IOURING_TAG_BATCH_READ  0x100
+#define IOURING_TAG_BATCH_WRITE 0x200
+
+typedef struct aeApiState {
+    int use_io_uring;
+    /* epoll fallback state */
+    int epfd;
+    struct epoll_event *epoll_events;
+    /* io_uring state */
+    struct io_uring ring;
+    int ring_entries;
+} aeApiState;
+
+static int aeApiCreate(aeEventLoop *eventLoop) {
+    aeApiState *state = zmalloc(sizeof(aeApiState));
+    if (!state) return -1;
+    memset(state, 0, sizeof(*state));
+    state->epfd = -1;
+
+    int entries = eventLoop->setsize;
+    if (entries < AE_IO_URING_RING_ENTRIES)
+        entries = AE_IO_URING_RING_ENTRIES;
+
+    if (io_uring_queue_init(entries, &state->ring, 0) == 0) {
+        state->use_io_uring = 1;
+        state->ring_entries = entries;
+        eventLoop->apidata = state;
+        return 0;
+    }
+
+    /* io_uring unavailable, fall back to epoll */
+    state->use_io_uring = 0;
+    state->epoll_events = zmalloc(sizeof(struct epoll_event) * eventLoop->setsize);
+    if (!state->epoll_events) {
+        zfree(state);
+        return -1;
+    }
+    state->epfd = epoll_create(1024);
+    if (state->epfd == -1) {
+        zfree(state->epoll_events);
+        zfree(state);
+        return -1;
+    }
+    anetCloexec(state->epfd);
+    eventLoop->apidata = state;
+    return 0;
+}
+
+static int aeApiResize(aeEventLoop *eventLoop, int setsize) {
+    aeApiState *state = eventLoop->apidata;
+    if (state->use_io_uring) return 0;
+    state->epoll_events = zrealloc(state->epoll_events,
+                                   sizeof(struct epoll_event) * setsize);
+    return 0;
+}
+
+static void aeApiFree(aeEventLoop *eventLoop) {
+    aeApiState *state = eventLoop->apidata;
+    if (state->use_io_uring) {
+        io_uring_queue_exit(&state->ring);
+    } else {
+        close(state->epfd);
+        zfree(state->epoll_events);
+    }
+    zfree(state);
+}
+
+static int aeApiAddEvent(aeEventLoop *eventLoop, int fd, int mask) {
+    aeApiState *state = eventLoop->apidata;
+
+    if (state->use_io_uring) {
+        int old_mask = eventLoop->events[fd].mask;
+        int full_mask = old_mask | mask;
+
+        /* Cancel existing multishot poll if modifying */
+        if (old_mask != AE_NONE) {
+            struct io_uring_sqe *sqe = io_uring_get_sqe(&state->ring);
+            if (!sqe) return -1;
+            io_uring_prep_poll_remove(sqe, IOURING_USERDATA(fd, old_mask));
+            io_uring_sqe_set_data64(sqe, 0);
+            io_uring_submit(&state->ring);
+
+            struct io_uring_cqe *cqe;
+            io_uring_wait_cqe(&state->ring, &cqe);
+            io_uring_cqe_seen(&state->ring, cqe);
+        }
+
+        struct io_uring_sqe *sqe = io_uring_get_sqe(&state->ring);
+        if (!sqe) return -1;
+
+        unsigned poll_mask = 0;
+        if (full_mask & AE_READABLE) poll_mask |= POLLIN;
+        if (full_mask & AE_WRITABLE) poll_mask |= POLLOUT;
+
+        io_uring_prep_poll_multishot(sqe, fd, poll_mask);
+        io_uring_sqe_set_data64(sqe, IOURING_USERDATA(fd, full_mask));
+        io_uring_submit(&state->ring);
+        return 0;
+    }
+
+    /* epoll fallback */
+    struct epoll_event ee = {0};
+    int op = eventLoop->events[fd].mask == AE_NONE ?
+            EPOLL_CTL_ADD : EPOLL_CTL_MOD;
+    ee.events = 0;
+    mask |= eventLoop->events[fd].mask;
+    if (mask & AE_READABLE) ee.events |= EPOLLIN;
+    if (mask & AE_WRITABLE) ee.events |= EPOLLOUT;
+    ee.data.fd = fd;
+    if (epoll_ctl(state->epfd, op, fd, &ee) == -1) return -1;
+    return 0;
+}
+
+static void aeApiDelEvent(aeEventLoop *eventLoop, int fd, int delmask) {
+    aeApiState *state = eventLoop->apidata;
+
+    if (state->use_io_uring) {
+        int old_mask = eventLoop->events[fd].mask;
+        int new_mask = old_mask & (~delmask);
+
+        struct io_uring_sqe *sqe = io_uring_get_sqe(&state->ring);
+        if (!sqe) return;
+        io_uring_prep_poll_remove(sqe, IOURING_USERDATA(fd, old_mask));
+        io_uring_sqe_set_data64(sqe, 0);
+        io_uring_submit(&state->ring);
+
+        struct io_uring_cqe *cqe;
+        io_uring_wait_cqe(&state->ring, &cqe);
+        io_uring_cqe_seen(&state->ring, cqe);
+
+        if (new_mask != AE_NONE) {
+            sqe = io_uring_get_sqe(&state->ring);
+            if (!sqe) return;
+
+            unsigned poll_mask = 0;
+            if (new_mask & AE_READABLE) poll_mask |= POLLIN;
+            if (new_mask & AE_WRITABLE) poll_mask |= POLLOUT;
+
+            io_uring_prep_poll_multishot(sqe, fd, poll_mask);
+            io_uring_sqe_set_data64(sqe, IOURING_USERDATA(fd, new_mask));
+            io_uring_submit(&state->ring);
+        }
+        return;
+    }
+
+    /* epoll fallback */
+    struct epoll_event ee = {0};
+    int mask = eventLoop->events[fd].mask & (~delmask);
+    ee.events = 0;
+    if (mask & AE_READABLE) ee.events |= EPOLLIN;
+    if (mask & AE_WRITABLE) ee.events |= EPOLLOUT;
+    ee.data.fd = fd;
+    if (mask != AE_NONE) {
+        epoll_ctl(state->epfd, EPOLL_CTL_MOD, fd, &ee);
+    } else {
+        epoll_ctl(state->epfd, EPOLL_CTL_DEL, fd, &ee);
+    }
+}
+
+static int aeApiPoll(aeEventLoop *eventLoop, struct timeval *tvp) {
+    aeApiState *state = eventLoop->apidata;
+
+    if (state->use_io_uring) {
+        int numevents = 0;
+        struct io_uring_cqe *cqe;
+
+        if (tvp != NULL) {
+            struct __kernel_timespec ts;
+            ts.tv_sec = tvp->tv_sec;
+            ts.tv_nsec = tvp->tv_usec * 1000;
+            int ret = io_uring_submit_and_wait_timeout(&state->ring, &cqe,
+                                                       1, &ts, NULL);
+            if (ret < 0 && ret != -ETIME && ret != -EINTR)
+                return 0;
+        } else {
+            int ret = io_uring_submit_and_wait(&state->ring, 1);
+            if (ret < 0 && ret != -EINTR)
+                return 0;
+        }
+
+        unsigned head;
+        int seen = 0;
+        io_uring_for_each_cqe(&state->ring, head, cqe) {
+            uint64_t ud = io_uring_cqe_get_data64(cqe);
+            int tag = IOURING_USERDATA_MASK(ud);
+            seen++;
+
+            /* Skip cancel completions and batch I/O completions */
+            if (ud == 0 || tag >= IOURING_TAG_BATCH_READ)
+                continue;
+
+            int fd = IOURING_USERDATA_FD(ud);
+            int res = cqe->res;
+            int mask = 0;
+
+            if (res < 0) {
+                mask = AE_READABLE | AE_WRITABLE;
+            } else {
+                if (res & POLLIN)  mask |= AE_READABLE;
+                if (res & POLLOUT) mask |= AE_WRITABLE;
+                if (res & POLLERR) mask |= AE_READABLE | AE_WRITABLE;
+                if (res & POLLHUP) mask |= AE_READABLE | AE_WRITABLE;
+            }
+
+            if (mask && numevents < eventLoop->setsize) {
+                eventLoop->fired[numevents].fd = fd;
+                eventLoop->fired[numevents].mask = mask;
+                numevents++;
+            }
+        }
+        io_uring_cq_advance(&state->ring, seen);
+        return numevents;
+    }
+
+    /* epoll fallback */
+    int retval, numevents = 0;
+    retval = epoll_wait(state->epfd, state->epoll_events, eventLoop->setsize,
+            tvp ? (tvp->tv_sec*1000 + (tvp->tv_usec + 999)/1000) : -1);
+    if (retval > 0) {
+        int j;
+        numevents = retval;
+        for (j = 0; j < numevents; j++) {
+            int mask = 0;
+            struct epoll_event *e = state->epoll_events + j;
+
+            if (e->events & EPOLLIN) mask |= AE_READABLE;
+            if (e->events & EPOLLOUT) mask |= AE_WRITABLE;
+            if (e->events & EPOLLERR) mask |= AE_WRITABLE | AE_READABLE;
+            if (e->events & EPOLLHUP) mask |= AE_WRITABLE | AE_READABLE;
+            eventLoop->fired[j].fd = e->data.fd;
+            eventLoop->fired[j].mask = mask;
+        }
+    } else if (retval == -1 && errno != EINTR) {
+        panic("aeApiPoll: epoll_wait, %s", strerror(errno));
+    }
+    return numevents;
+}
+
+static char *aeApiName(void) {
+    return "io_uring";
+}
diff --git a/src/config.c b/src/config.c
@@ -3206,6 +3206,12 @@ standardConfig static_configs[] = {
     createIntConfig("databases", NULL, IMMUTABLE_CONFIG, 1, INT_MAX, server.dbnum, 16, INTEGER_CONFIG, NULL, NULL),
     createIntConfig("port", NULL, MODIFIABLE_CONFIG, 0, 65535, server.port, 6379, INTEGER_CONFIG, NULL, updatePort), /* TCP port. */
     createIntConfig("io-threads", NULL, DEBUG_CONFIG | IMMUTABLE_CONFIG, 1, 128, server.io_threads_num, 1, INTEGER_CONFIG, NULL, NULL), /* Single threaded by default */
+#ifdef HAVE_IO_URING
+    createBoolConfig("io-uring-enabled", NULL, IMMUTABLE_CONFIG, server.io_uring_enabled, 1, NULL, NULL),
+    createBoolConfig("io-uring-batch-writes", NULL, IMMUTABLE_CONFIG, server.io_uring_batch_writes, 1, NULL, NULL),
+    createBoolConfig("io-uring-batch-reads", NULL, IMMUTABLE_CONFIG, server.io_uring_batch_reads, 0, NULL, NULL),
+    createIntConfig("io-uring-sq-size", NULL, IMMUTABLE_CONFIG, 64, 16384, server.io_uring_sq_size, 1024, INTEGER_CONFIG, NULL, NULL),
+#endif
     createIntConfig("prefetch-batch-max-size", NULL, MODIFIABLE_CONFIG | HIDDEN_CONFIG, 0, PREFETCH_BATCH_MAX_SIZE, server.prefetch_batch_max_size, 16, INTEGER_CONFIG, NULL, NULL),
     createIntConfig("auto-aof-rewrite-percentage", NULL, MODIFIABLE_CONFIG, 0, INT_MAX, server.aof_rewrite_perc, 100, INTEGER_CONFIG, NULL, NULL),
     createIntConfig("cluster-replica-validity-factor", "cluster-slave-validity-factor", MODIFIABLE_CONFIG, 0, INT_MAX, server.cluster_slave_validity_factor, 10, INTEGER_CONFIG, NULL, NULL), /* Slave max data age factor. */

diff --git a/src/config.h b/src/config.h
@@ -84,6 +84,8 @@
 /* Test for polling API */
 #ifdef __linux__
 #define HAVE_EPOLL 1
+/* HAVE_IO_URING is defined via Makefile when USE_IO_URING=yes.
+ * Requires Linux 5.6+ and liburing. */
 #endif
 
 /* Test for accept4() */