io_uring/net: add iovec recycling

Right now the io_async_msghdr is recycled to avoid the overhead of
allocating+freeing it for every request. But the iovec is not included,
hence that will be allocated and freed for each transfer regardless.
This commit enables recyling of the iovec between io_async_msghdr
recycles. This avoids alloc+free for each one if an iovec is used, and
on top of that, it extends the cache hot nature of msg to the iovec as
well.

Also enables KASAN for the iovec entries, so that reuse can be detected
even while they are in the cache.

The io_async_msghdr also shrinks from 376 -> 288 bytes, an 88 byte
saving (or ~23% smaller), as the fast_iovec entry is dropped from 8
entries to a single entry. There's no point keeping a big fast iovec
entry, if iovecs aren't being allocated and freed continually.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 7 insertions, 6 deletions

diff --git a/io_uring/net.h b/io_uring/net.h
index f99ebb9dc0bb..0aef1c992aee 100644
--- a/io_uring/net.h
+++ b/io_uring/net.h
@@ -8,17 +8,18 @@
 struct io_async_msghdr {
 #if defined(CONFIG_NET)
 	union {
-		struct iovec		fast_iov[UIO_FASTIOV];
+		struct iovec			fast_iov;
 		struct {
-			struct iovec	fast_iov_one;
-			__kernel_size_t	controllen;
-			int		namelen;
-			__kernel_size_t	payloadlen;
+			struct io_cache_entry	cache;
+			/* entry size of ->free_iov, if valid */
+			int			free_iov_nr;
 		};
-		struct io_cache_entry	cache;
 	};
 	/* points to an allocated iov, if NULL we use fast_iov instead */
 	struct iovec			*free_iov;
+	__kernel_size_t			controllen;
+	__kernel_size_t			payloadlen;
+	int				namelen;
 	struct sockaddr __user		*uaddr;
 	struct msghdr			msg;
 	struct sockaddr_storage		addr;