@@ -270,6 +270,14 @@ struct io_ring_ctx {
struct xarray personalities;
u32 pers_next;
+#ifdef CONFIG_NET_RX_BUSY_POLL
+ struct list_head napi_list; /* track busy poll napi_id */
+ spinlock_t napi_lock; /* napi_list lock */
+
+ unsigned int napi_busy_poll_to; /* napi busy poll default timeout */
+ bool napi_prefer_busy_poll;
+#endif
+
struct {
/*
* We cache a range of free CQEs we can use, once exhausted it
@@ -90,6 +90,7 @@
#include "rsrc.h"
#include "cancel.h"
#include "net.h"
+#include "napi.h"
#include "notif.h"
#include "timeout.h"
@@ -332,6 +333,14 @@ static __cold struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
INIT_WQ_LIST(&ctx->locked_free_list);
INIT_DELAYED_WORK(&ctx->fallback_work, io_fallback_req_func);
INIT_WQ_LIST(&ctx->submit_state.compl_reqs);
+
+#ifdef CONFIG_NET_RX_BUSY_POLL
+ INIT_LIST_HEAD(&ctx->napi_list);
+ spin_lock_init(&ctx->napi_lock);
+ ctx->napi_prefer_busy_poll = false;
+ ctx->napi_busy_poll_to = READ_ONCE(sysctl_net_busy_poll);
+#endif
+
return ctx;
err:
kfree(ctx->dummy_ubuf);
@@ -2308,6 +2317,11 @@ struct io_wait_queue {
struct io_ring_ctx *ctx;
unsigned cq_tail;
unsigned nr_timeouts;
+
+#ifdef CONFIG_NET_RX_BUSY_POLL
+ unsigned int napi_busy_poll_to;
+ bool napi_prefer_busy_poll;
+#endif
};
static inline bool io_has_work(struct io_ring_ctx *ctx)
@@ -2381,6 +2395,200 @@ static inline int io_cqring_wait_schedule(struct io_ring_ctx *ctx,
return 1;
}
+#ifdef CONFIG_NET_RX_BUSY_POLL
+#define NAPI_TIMEOUT (60 * SEC_CONVERSION)
+
+struct io_napi_entry {
+ struct list_head list;
+ unsigned int napi_id;
+ unsigned long timeout;
+};
+
+static bool io_napi_busy_loop_on(struct io_ring_ctx *ctx)
+{
+ return READ_ONCE(ctx->napi_busy_poll_to);
+}
+
+/*
+ * io_napi_add() - Add napi id to the busy poll list
+ * @file: file pointer for socket
+ * @ctx: io-uring context
+ *
+ * Add the napi id of the socket to the napi busy poll list.
+ */
+void io_napi_add(struct file *file, struct io_ring_ctx *ctx)
+{
+ unsigned int napi_id;
+ struct socket *sock;
+ struct sock *sk;
+ struct io_napi_entry *ne;
+
+ if (!io_napi_busy_loop_on(ctx))
+ return;
+
+ sock = sock_from_file(file);
+ if (!sock)
+ return;
+
+ sk = sock->sk;
+ if (!sk)
+ return;
+
+ napi_id = READ_ONCE(sk->sk_napi_id);
+
+ /* Non-NAPI IDs can be rejected */
+ if (napi_id < MIN_NAPI_ID)
+ return;
+
+ spin_lock(&ctx->napi_lock);
+ list_for_each_entry(ne, &ctx->napi_list, list) {
+ if (ne->napi_id == napi_id) {
+ ne->timeout = jiffies + NAPI_TIMEOUT;
+ goto out;
+ }
+ }
+
+ ne = kmalloc(sizeof(*ne), GFP_NOWAIT);
+ if (!ne)
+ goto out;
+
+ ne->napi_id = napi_id;
+ ne->timeout = jiffies + NAPI_TIMEOUT;
+ list_add_tail(&ne->list, &ctx->napi_list);
+
+out:
+ spin_unlock(&ctx->napi_lock);
+}
+
+static void io_napi_free_list(struct io_ring_ctx *ctx)
+{
+ spin_lock(&ctx->napi_lock);
+ while (!list_empty(&ctx->napi_list)) {
+ struct io_napi_entry *ne =
+ list_first_entry(&ctx->napi_list,
+ struct io_napi_entry, list);
+
+ list_del(&ne->list);
+ kfree(ne);
+ }
+ spin_unlock(&ctx->napi_lock);
+}
+
+static void io_napi_adjust_busy_loop_timeout(unsigned int poll_to,
+ struct timespec64 *ts,
+ unsigned int *new_poll_to)
+{
+ struct timespec64 pollto = ns_to_timespec64(1000 * (s64)poll_to);
+
+ if (timespec64_compare(ts, &pollto) > 0) {
+ *ts = timespec64_sub(*ts, pollto);
+ *new_poll_to = poll_to;
+ } else {
+ u64 to = timespec64_to_ns(ts);
+
+ do_div(to, 1000);
+ *new_poll_to = to;
+ ts->tv_sec = 0;
+ ts->tv_nsec = 0;
+ }
+}
+
+static inline bool io_napi_busy_loop_timeout(unsigned long start_time,
+ unsigned long bp_usec)
+{
+ if (bp_usec) {
+ unsigned long end_time = start_time + bp_usec;
+ unsigned long now = busy_loop_current_time();
+
+ return time_after(now, end_time);
+ }
+ return true;
+}
+
+static inline void io_napi_check_entry_timeout(struct io_napi_entry *ne)
+{
+ if (time_after(jiffies, ne->timeout)) {
+ list_del(&ne->list);
+ kfree(ne);
+ }
+}
+
+/*
+ * io_napi_busy_loop() - napi busy poll loop
+ * @napi_list : list of napi_id's supporting busy polling
+ * @napi_prefer_busy_poll: prefer napi busy polling
+ *
+ * This invokes the napi busy poll loop if sockets have been added to the
+ * napi busy poll list.
+ *
+ * Returns if all napi-id's in the list have been processed.
+ */
+bool io_napi_busy_loop(struct list_head *napi_list, bool prefer_busy_poll)
+{
+ struct io_napi_entry *ne;
+ struct io_napi_entry *n;
+
+ list_for_each_entry_safe(ne, n, napi_list, list) {
+ napi_busy_loop(ne->napi_id, NULL, NULL, prefer_busy_poll,
+ BUSY_POLL_BUDGET);
+ io_napi_check_entry_timeout(ne);
+ }
+
+ return !list_empty(napi_list);
+}
+
+static bool io_napi_busy_loop_end(void *p, unsigned long start_time)
+{
+ struct io_wait_queue *iowq = p;
+
+ return signal_pending(current) ||
+ io_should_wake(iowq) ||
+ io_napi_busy_loop_timeout(start_time, iowq->napi_busy_poll_to);
+}
+
+static void io_napi_blocking_busy_loop(struct list_head *napi_list,
+ struct io_wait_queue *iowq)
+{
+ unsigned long start_time = list_is_singular(napi_list)
+ ? 0
+ : busy_loop_current_time();
+
+ do {
+ if (list_is_singular(napi_list)) {
+ struct io_napi_entry *ne =
+ list_first_entry(napi_list,
+ struct io_napi_entry, list);
+
+ napi_busy_loop(ne->napi_id, io_napi_busy_loop_end, iowq,
+ iowq->napi_prefer_busy_poll, BUSY_POLL_BUDGET);
+ io_napi_check_entry_timeout(ne);
+ break;
+ }
+ } while (io_napi_busy_loop(napi_list, iowq->napi_prefer_busy_poll) &&
+ !io_napi_busy_loop_end(iowq, start_time));
+}
+
+static void io_napi_putback_list(struct io_ring_ctx *ctx,
+ struct list_head *napi_list)
+{
+ struct io_napi_entry *cne;
+ struct io_napi_entry *lne;
+
+ spin_lock(&ctx->napi_lock);
+ list_for_each_entry(cne, &ctx->napi_list, list) {
+ list_for_each_entry(lne, napi_list, list) {
+ if (cne->napi_id == lne->napi_id) {
+ list_del(&lne->list);
+ kfree(lne);
+ break;
+ }
+ }
+ }
+ list_splice(napi_list, &ctx->napi_list);
+ spin_unlock(&ctx->napi_lock);
+}
+#endif
+
/*
* Wait until events become available, if we don't already have some. The
* application must reap them itself, as they reside on the shared cq ring.
@@ -2393,6 +2601,9 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events,
struct io_rings *rings = ctx->rings;
ktime_t timeout = KTIME_MAX;
int ret;
+#ifdef CONFIG_NET_RX_BUSY_POLL
+ LIST_HEAD(local_napi_list);
+#endif
if (!io_allowed_run_tw(ctx))
return -EEXIST;
@@ -2422,12 +2633,34 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events,
return ret;
}
+#ifdef CONFIG_NET_RX_BUSY_POLL
+ iowq.napi_busy_poll_to = 0;
+ iowq.napi_prefer_busy_poll = READ_ONCE(ctx->napi_prefer_busy_poll);
+
+ if (!(ctx->flags & IORING_SETUP_SQPOLL)) {
+ spin_lock(&ctx->napi_lock);
+ list_splice_init(&ctx->napi_list, &local_napi_list);
+ spin_unlock(&ctx->napi_lock);
+ }
+#endif
+
if (uts) {
struct timespec64 ts;
if (get_timespec64(&ts, uts))
return -EFAULT;
+
+#ifdef CONFIG_NET_RX_BUSY_POLL
+ if (!list_empty(&local_napi_list)) {
+ io_napi_adjust_busy_loop_timeout(READ_ONCE(ctx->napi_busy_poll_to),
+ &ts, &iowq.napi_busy_poll_to);
+ }
+#endif
timeout = ktime_add_ns(timespec64_to_ktime(ts), ktime_get_ns());
+#ifdef CONFIG_NET_RX_BUSY_POLL
+ } else if (!list_empty(&local_napi_list)) {
+ iowq.napi_busy_poll_to = READ_ONCE(ctx->napi_busy_poll_to);
+#endif
}
init_waitqueue_func_entry(&iowq.wq, io_wake_function);
@@ -2438,6 +2671,15 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events,
iowq.cq_tail = READ_ONCE(ctx->rings->cq.head) + min_events;
trace_io_uring_cqring_wait(ctx, min_events);
+
+#ifdef CONFIG_NET_RX_BUSY_POLL
+ if (iowq.napi_busy_poll_to)
+ io_napi_blocking_busy_loop(&local_napi_list, &iowq);
+
+ if (!list_empty(&local_napi_list))
+ io_napi_putback_list(ctx, &local_napi_list);
+#endif
+
do {
/* if we can't even flush overflow, don't wait for more */
if (!io_cqring_overflow_flush(ctx)) {
@@ -2637,6 +2879,9 @@ static __cold void io_ring_ctx_free(struct io_ring_ctx *ctx)
io_req_caches_free(ctx);
if (ctx->hash_map)
io_wq_put_hash(ctx->hash_map);
+#ifdef CONFIG_NET_RX_BUSY_POLL
+ io_napi_free_list(ctx);
+#endif
kfree(ctx->cancel_table.hbs);
kfree(ctx->cancel_table_locked.hbs);
kfree(ctx->dummy_ubuf);
new file mode 100644
@@ -0,0 +1,22 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef IOU_NAPI_H
+#define IOU_NAPI_H
+
+#include <linux/kernel.h>
+#include <linux/io_uring.h>
+#include <net/busy_poll.h>
+
+#ifdef CONFIG_NET_RX_BUSY_POLL
+
+void io_napi_add(struct file *file, struct io_ring_ctx *ctx);
+bool io_napi_busy_loop(struct list_head *napi_list, bool prefer_busy_poll);
+
+#else
+
+static inline void io_napi_add(struct file *file, struct io_ring_ctx *ctx)
+{
+}
+
+#endif
+#endif
@@ -15,6 +15,7 @@
#include "io_uring.h"
#include "refs.h"
+#include "napi.h"
#include "opdef.h"
#include "kbuf.h"
#include "poll.h"
@@ -250,6 +251,7 @@ static int io_poll_check_events(struct io_kiocb *req, bool *locked)
io_req_set_res(req, mask, 0);
return IOU_POLL_REMOVE_POLL_USE_RES;
}
+ io_napi_add(req->file, ctx);
} else {
ret = io_poll_issue(req, locked);
if (ret == IOU_STOP_MULTISHOT)
@@ -571,6 +573,7 @@ static int __io_arm_poll_handler(struct io_kiocb *req,
__io_poll_execute(req, mask);
return 0;
}
+ io_napi_add(req->file, req->ctx);
if (ipt->owning) {
/*
@@ -15,6 +15,7 @@
#include <uapi/linux/io_uring.h>
#include "io_uring.h"
+#include "napi.h"
#include "sqpoll.h"
#define IORING_SQPOLL_CAP_ENTRIES_VALUE 8
@@ -193,6 +194,15 @@ static int __io_sq_thread(struct io_ring_ctx *ctx, bool cap_entries)
ret = io_submit_sqes(ctx, to_submit);
mutex_unlock(&ctx->uring_lock);
+#ifdef CONFIG_NET_RX_BUSY_POLL
+ spin_lock(&ctx->napi_lock);
+ if (!list_empty(&ctx->napi_list) &&
+ READ_ONCE(ctx->napi_busy_poll_to) > 0 &&
+ io_napi_busy_loop(&ctx->napi_list, ctx->napi_prefer_busy_poll))
+ ++ret;
+ spin_unlock(&ctx->napi_lock);
+#endif
+
if (to_submit && wq_has_sleeper(&ctx->sqo_sq_wait))
wake_up(&ctx->sqo_sq_wait);
if (creds)
This adds the napi busy polling support in io_uring.c. It adds a new napi_list to the io_ring_ctx structure. This list contains the list of napi_id's that are currently enabled for busy polling. The list is synchronized by the new napi_lock spin lock. The current default napi busy polling time is stored in napi_busy_poll_to. If napi busy polling is not enabled, the value is 0. The NAPI_TIMEOUT is stored as a timeout to make sure that the time a napi entry is stored in the napi list is limited. The busy poll timeout is also stored as part of the io_wait_queue. This is necessary as for sq polling the poll interval needs to be adjusted and the napi callback allows only to pass in one value. This has been tested with two simple programs from the liburing library repository: the napi client and the napi server program. The client sends a request, which has a timestamp in its payload and the server replies with the same payload. The client calculates the roundtrip time and stores it to calcualte the results. The client is running on host1 and the server is running on host 2 (in the same rack). The measured times below are roundtrip times. They are average times over 5 runs each. Each run measures 1 million roundtrips. no rx coal rx coal: frames=88,usecs=33 Default 57us 56us client_poll=100us 47us 46us server_poll=100us 51us 46us client_poll=100us+ 40us 40us server_poll=100us client_poll=100us+ 41us 39us server_poll=100us+ prefer napi busy poll on client client_poll=100us+ 41us 39us server_poll=100us+ prefer napi busy poll on server client_poll=100us+ 41us 39us server_poll=100us+ prefer napi busy poll on client + server Signed-off-by: Stefan Roesch <shr@devkernel.io> Suggested-by: Olivier Langlois <olivier@trillion01.com> --- include/linux/io_uring_types.h | 8 ++ io_uring/io_uring.c | 245 +++++++++++++++++++++++++++++++++ io_uring/napi.h | 22 +++ io_uring/poll.c | 3 + io_uring/sqpoll.c | 10 ++ 5 files changed, 288 insertions(+) create mode 100644 io_uring/napi.h