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net: Introduce recvmmsg socket syscall

Browse source 
Meaning receive multiple messages, reducing the number of syscalls and
net stack entry/exit operations.

Next patches will introduce mechanisms where protocols that want to
optimize this operation will provide an unlocked_recvmsg operation.

This takes into account comments made by:

. Paul Moore: sock_recvmsg is called only for the first datagram,
  sock_recvmsg_nosec is used for the rest.

. Caitlin Bestler: recvmmsg now has a struct timespec timeout, that
  works in the same fashion as the ppoll one.

  If the underlying protocol returns a datagram with MSG_OOB set, this
  will make recvmmsg return right away with as many datagrams (+ the OOB
  one) it has received so far.

. Rémi Denis-Courmont & Steven Whitehouse: If we receive N < vlen
  datagrams and then recvmsg returns an error, recvmmsg will return
  the successfully received datagrams, store the error and return it
  in the next call.

This paves the way for a subsequent optimization, sk_prot->unlocked_recvmsg,
where we will be able to acquire the lock only at batch start and end, not at
every underlying recvmsg call.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Arnaldo Carvalho de Melo 2009-10-12 23:40:10 -07:00 • committed by David S. Miller
commit a2e2725541
25 changed files with 261 additions and 50 deletions
Download patch file Download diff file Expand all files Collapse all files

1
include/linux/net.h
View file

@ -41,6 +41,7 @@
#define SYS_SENDMSG 16 /* sys_sendmsg(2) */
#define SYS_RECVMSG 17 /* sys_recvmsg(2) */
#define SYS_ACCEPT4 18 /* sys_accept4(2) */
#define SYS_RECVMMSG 19 /* sys_recvmmsg(2) */
typedef enum {
SS_FREE = 0, /* not allocated */

10
include/linux/socket.h
View file

@ -65,6 +65,12 @@ struct msghdr {
unsigned msg_flags;
};
/* For recvmmsg/sendmmsg */
struct mmsghdr {
struct msghdr msg_hdr;
unsigned msg_len;
};
/*
* POSIX 1003.1g - ancillary data object information
* Ancillary data consits of a sequence of pairs of
@ -312,6 +318,10 @@ extern int move_addr_to_user(struct sockaddr *kaddr, int klen, void __user *uadd
extern int move_addr_to_kernel(void __user *uaddr, int ulen, struct sockaddr *kaddr);
extern int put_cmsg(struct msghdr*, int level, int type, int len, void *data);
struct timespec;
extern int __sys_recvmmsg(int fd, struct mmsghdr __user *mmsg, unsigned int vlen,
unsigned int flags, struct timespec *timeout);
#endif
#endif /* not kernel and not glibc */
#endif /* _LINUX_SOCKET_H */

4
include/linux/syscalls.h
View file

@ -25,6 +25,7 @@ struct linux_dirent64;
struct list_head;
struct msgbuf;
struct msghdr;
struct mmsghdr;
struct msqid_ds;
struct new_utsname;
struct nfsctl_arg;
@ -677,6 +678,9 @@ asmlinkage long sys_recv(int, void __user *, size_t, unsigned);
asmlinkage long sys_recvfrom(int, void __user *, size_t, unsigned,
struct sockaddr __user *, int __user *);
asmlinkage long sys_recvmsg(int fd, struct msghdr __user *msg, unsigned flags);
asmlinkage long sys_recvmmsg(int fd, struct mmsghdr __user *msg,
unsigned int vlen, unsigned flags,
struct timespec __user *timeout);
asmlinkage long sys_socket(int, int, int);
asmlinkage long sys_socketpair(int, int, int, int __user *);
asmlinkage long sys_socketcall(int call, unsigned long __user *args);