[PATCH 4/4] io_uring: add netmsg cache

Jens Axboe
2022-07-07T23:24:25Z

For recvmsg/sendmsg, if they don't complete inline, we currently need
to allocate a struct io_async_msghdr for each request. This is a
somewhat large struct.

Hook up sendmsg/recvmsg to use the io_alloc_cache. This reduces the
alloc + free overhead considerably, yielding 4-5% of extra performance
running netbench.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
include/linux/io_uring_types.h | 6 ++-
io_uring/io_uring.c | 3 ++
io_uring/net.c | 73 +++++++++++++++++++++++++++++-----
io_uring/net.h | 11 ++++-
4 files changed, 81 insertions(+), 12 deletions(-)

diff --git a/include/linux/io_uring_types.h b/include/linux/io_uring_types.h
index bf8f95332eda..d54b8b7e0746 100644
--- a/include/linux/io_uring_types.h
+++ b/include/linux/io_uring_types.h
@@ -222,8 +222,7 @@ struct io_ring_ctx {
struct io_hash_table cancel_table_locked;
struct list_head cq_overflow_list;
struct io_alloc_cache apoll_cache;
- struct xarray personalities;
- u32 pers_next;
+ struct io_alloc_cache netmsg_cache;
} ____cacheline_aligned_in_smp;

/* IRQ completion list, under ->completion_lock */
@@ -241,6 +240,9 @@ struct io_ring_ctx {
unsigned int file_alloc_start;
unsigned int file_alloc_end;

+ struct xarray personalities;
+ u32 pers_next;
+
struct {
/*
* We cache a range of free CQEs we can use, once exhausted it
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index b5098773d924..32110c5b4059 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -89,6 +89,7 @@
#include "kbuf.h"
#include "rsrc.h"
#include "cancel.h"
+#include "net.h"

#include "timeout.h"
#include "poll.h"
@@ -297,6 +298,7 @@ static __cold struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
INIT_LIST_HEAD(&ctx->cq_overflow_list);
INIT_LIST_HEAD(&ctx->io_buffers_cache);
io_alloc_cache_init(&ctx->apoll_cache);
+ io_alloc_cache_init(&ctx->netmsg_cache);
init_completion(&ctx->ref_comp);
xa_init_flags(&ctx->personalities, XA_FLAGS_ALLOC1);
mutex_init(&ctx->uring_lock);
@@ -2473,6 +2475,7 @@ static __cold void io_ring_ctx_free(struct io_ring_ctx *ctx)
__io_cqring_overflow_flush(ctx, true);
io_eventfd_unregister(ctx);
io_flush_apoll_cache(ctx);
+ io_flush_netmsg_cache(ctx);
mutex_unlock(&ctx->uring_lock);
io_destroy_buffers(ctx);
if (ctx->sq_creds)
diff --git a/io_uring/net.c b/io_uring/net.c
index 6679069eeef1..ba7e94ff287c 100644
--- a/io_uring/net.c
+++ b/io_uring/net.c
@@ -12,6 +12,7 @@

#include "io_uring.h"
#include "kbuf.h"
+#include "alloc_cache.h"
#include "net.h"

#if defined(CONFIG_NET)
@@ -97,18 +98,57 @@ static bool io_net_retry(struct socket *sock, int flags)
return sock->type == SOCK_STREAM || sock->type == SOCK_SEQPACKET;
}

+static void io_netmsg_recycle(struct io_kiocb *req, unsigned int issue_flags)
+{
+ struct io_async_msghdr *hdr = req->async_data;
+
+ if (!hdr || issue_flags & IO_URING_F_UNLOCKED)
+ return;
+
+ if (io_alloc_cache_store(&req->ctx->netmsg_cache)) {
+ hlist_add_head(&hdr->cache_list, &req->ctx->netmsg_cache.list);
+ req->async_data = NULL;
+ req->flags &= ~REQ_F_ASYNC_DATA;
+ }
+}
+
+static struct io_async_msghdr *io_recvmsg_alloc_async(struct io_kiocb *req,
+ unsigned int issue_flags)
+{
+ struct io_ring_ctx *ctx = req->ctx;
+
+ if (!(issue_flags & IO_URING_F_UNLOCKED) &&
+ !hlist_empty(&ctx->netmsg_cache.list)) {
+ struct io_async_msghdr *hdr;
+
+ hdr = hlist_entry(ctx->netmsg_cache.list.first,
+ struct io_async_msghdr, cache_list);
+ ctx->netmsg_cache.nr_cached--;
+ hlist_del(&hdr->cache_list);
+ req->flags |= REQ_F_ASYNC_DATA;
+ req->async_data = hdr;
+ return hdr;
+ }
+
+ if (!io_alloc_async_data(req))
+ return req->async_data;
+
+ return NULL;
+}
+
static int io_setup_async_msg(struct io_kiocb *req,
- struct io_async_msghdr *kmsg)
+ struct io_async_msghdr *kmsg,
+ unsigned int issue_flags)
{
struct io_async_msghdr *async_msg = req->async_data;

if (async_msg)
return -EAGAIN;
- if (io_alloc_async_data(req)) {
+ async_msg = io_recvmsg_alloc_async(req, issue_flags);
+ if (!async_msg) {
kfree(kmsg->free_iov);
return -ENOMEM;
}
- async_msg = req->async_data;
req->flags |= REQ_F_NEED_CLEANUP;
memcpy(async_msg, kmsg, sizeof(*kmsg));
async_msg->msg.msg_name = &async_msg->addr;
@@ -195,7 +235,7 @@ int io_sendmsg(struct io_kiocb *req, unsigned int issue_flags)

if (!(req->flags & REQ_F_POLLED) &&
(sr->flags & IORING_RECVSEND_POLL_FIRST))
- return io_setup_async_msg(req, kmsg);
+ return io_setup_async_msg(req, kmsg, issue_flags);

flags = sr->msg_flags;
if (issue_flags & IO_URING_F_NONBLOCK)
@@ -207,13 +247,13 @@ int io_sendmsg(struct io_kiocb *req, unsigned int issue_flags)

if (ret < min_ret) {
if (ret == -EAGAIN && (issue_flags & IO_URING_F_NONBLOCK))
- return io_setup_async_msg(req, kmsg);
+ return io_setup_async_msg(req, kmsg, issue_flags);
if (ret == -ERESTARTSYS)
ret = -EINTR;
if (ret > 0 && io_net_retry(sock, flags)) {
sr->done_io += ret;
req->flags |= REQ_F_PARTIAL_IO;
- return io_setup_async_msg(req, kmsg);
+ return io_setup_async_msg(req, kmsg, issue_flags);
}
req_set_fail(req);
}
@@ -221,6 +261,7 @@ int io_sendmsg(struct io_kiocb *req, unsigned int issue_flags)
if (kmsg->free_iov)
kfree(kmsg->free_iov);
req->flags &= ~REQ_F_NEED_CLEANUP;
+ io_netmsg_recycle(req, issue_flags);
if (ret >= 0)
ret += sr->done_io;
else if (sr->done_io)
@@ -495,7 +536,7 @@ int io_recvmsg(struct io_kiocb *req, unsigned int issue_flags)

if (!(req->flags & REQ_F_POLLED) &&
(sr->flags & IORING_RECVSEND_POLL_FIRST))
- return io_setup_async_msg(req, kmsg);
+ return io_setup_async_msg(req, kmsg, issue_flags);

if (io_do_buffer_select(req)) {
void __user *buf;
@@ -519,13 +560,13 @@ int io_recvmsg(struct io_kiocb *req, unsigned int issue_flags)
ret = __sys_recvmsg_sock(sock, &kmsg->msg, sr->umsg, kmsg->uaddr, flags);
if (ret < min_ret) {
if (ret == -EAGAIN && force_nonblock)
- return io_setup_async_msg(req, kmsg);
+ return io_setup_async_msg(req, kmsg, issue_flags);
if (ret == -ERESTARTSYS)
ret = -EINTR;
if (ret > 0 && io_net_retry(sock, flags)) {
sr->done_io += ret;
req->flags |= REQ_F_PARTIAL_IO;
- return io_setup_async_msg(req, kmsg);
+ return io_setup_async_msg(req, kmsg, issue_flags);
}
req_set_fail(req);
} else if ((flags & MSG_WAITALL) && (kmsg->msg.msg_flags & (MSG_TRUNC | MSG_CTRUNC))) {
@@ -535,6 +576,7 @@ int io_recvmsg(struct io_kiocb *req, unsigned int issue_flags)
/* fast path, check for non-NULL to avoid function call */
if (kmsg->free_iov)
kfree(kmsg->free_iov);
+ io_netmsg_recycle(req, issue_flags);
req->flags &= ~REQ_F_NEED_CLEANUP;
if (ret > 0)
ret += sr->done_io;
@@ -848,4 +890,17 @@ int io_connect(struct io_kiocb *req, unsigned int issue_flags)
io_req_set_res(req, ret, 0);
return IOU_OK;
}
+
+void io_flush_netmsg_cache(struct io_ring_ctx *ctx)
+{
+ while (!hlist_empty(&ctx->netmsg_cache.list)) {
+ struct io_async_msghdr *hdr;
+
+ hdr = hlist_entry(ctx->netmsg_cache.list.first,
+ struct io_async_msghdr, cache_list);
+ hlist_del(&hdr->cache_list);
+ kfree(hdr);
+ }
+ ctx->netmsg_cache.nr_cached = 0;
+}
#endif
diff --git a/io_uring/net.h b/io_uring/net.h
index 81d71d164770..576efb602c7f 100644
--- a/io_uring/net.h
+++ b/io_uring/net.h
@@ -5,7 +5,10 @@

#if defined(CONFIG_NET)
struct io_async_msghdr {
- struct iovec fast_iov[UIO_FASTIOV];
+ union {
+ struct iovec fast_iov[UIO_FASTIOV];
+ struct hlist_node cache_list;
+ };
/* points to an allocated iov, if NULL we use fast_iov instead */
struct iovec *free_iov;
struct sockaddr __user *uaddr;
@@ -40,4 +43,10 @@ int io_socket(struct io_kiocb *req, unsigned int issue_flags);
int io_connect_prep_async(struct io_kiocb *req);
int io_connect_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);
int io_connect(struct io_kiocb *req, unsigned int issue_flags);
+
+void io_flush_netmsg_cache(struct io_ring_ctx *ctx);
+#else
+static inline void io_flush_netmsg_cache(struct io_ring_ctx *ctx)
+{
+}
#endif
--
2.35.1