svn commit: r241931 - in head/sys: conf kern
Andre Oppermann
andre at FreeBSD.org
Tue Oct 23 14:19:45 UTC 2012
Author: andre
Date: Tue Oct 23 14:19:44 2012
New Revision: 241931
URL: http://svn.freebsd.org/changeset/base/241931
Log:
Replace the ill-named ZERO_COPY_SOCKET kernel option with two
more appropriate named kernel options for the very distinct
send and receive path.
"options SOCKET_SEND_COW" enables VM page copy-on-write based
sending of data on an outbound socket.
NB: The COW based send mechanism is not safe and may result
in kernel crashes.
"options SOCKET_RECV_PFLIP" enables VM kernel/userspace page
flipping for special disposable pages attached as external
storage to mbufs.
Only the naming of the kernel options is changed and their
corresponding #ifdef sections are adjusted. No functionality
is added or removed.
Discussed with: alc (mechanism and limitations of send side COW)
Modified:
head/sys/conf/NOTES
head/sys/conf/options
head/sys/kern/subr_uio.c
head/sys/kern/uipc_socket.c
Modified: head/sys/conf/NOTES
==============================================================================
--- head/sys/conf/NOTES Tue Oct 23 12:39:17 2012 (r241930)
+++ head/sys/conf/NOTES Tue Oct 23 14:19:44 2012 (r241931)
@@ -964,12 +964,20 @@ options TCP_SIGNATURE #include support
# a smooth scheduling of the traffic.
options DUMMYNET
-# Zero copy sockets support. This enables "zero copy" for sending and
-# receiving data via a socket. The send side works for any type of NIC,
-# the receive side only works for NICs that support MTUs greater than the
-# page size of your architecture and that support header splitting. See
-# zero_copy(9) for more details.
-options ZERO_COPY_SOCKETS
+# "Zero copy" sockets support is split into the send and receive path
+# which operate very differently.
+# For the send path the VM page with the data is wired into the kernel
+# and marked as COW (copy-on-write). If the application touches the
+# data while it is still in the send socket buffer the page is copied
+# and divorced from its kernel wiring (no longer zero copy).
+# The receive side requires explicit NIC driver support to create
+# disposable pages which are flipped from kernel to user-space VM.
+# See zero_copy(9) for more details.
+# XXX: The COW based send mechanism is not safe and may result in
+# kernel crashes.
+# XXX: None of the current NIC drivers support disposeable pages.
+options SOCKET_SEND_COW
+options SOCKET_RECV_PFLIP
#####################################################################
# FILESYSTEM OPTIONS
Modified: head/sys/conf/options
==============================================================================
--- head/sys/conf/options Tue Oct 23 12:39:17 2012 (r241930)
+++ head/sys/conf/options Tue Oct 23 14:19:44 2012 (r241931)
@@ -520,7 +520,8 @@ NGATM_CCATM opt_netgraph.h
# DRM options
DRM_DEBUG opt_drm.h
-ZERO_COPY_SOCKETS opt_zero.h
+SOCKET_SEND_COW opt_zero.h
+SOCKET_RECV_PFLIP opt_zero.h
TI_SF_BUF_JUMBO opt_ti.h
TI_JUMBO_HDRSPLIT opt_ti.h
BCE_JUMBO_HDRSPLIT opt_bce.h
Modified: head/sys/kern/subr_uio.c
==============================================================================
--- head/sys/kern/subr_uio.c Tue Oct 23 12:39:17 2012 (r241930)
+++ head/sys/kern/subr_uio.c Tue Oct 23 14:19:44 2012 (r241931)
@@ -57,7 +57,7 @@ __FBSDID("$FreeBSD$");
#include <vm/vm_extern.h>
#include <vm/vm_page.h>
#include <vm/vm_map.h>
-#ifdef ZERO_COPY_SOCKETS
+#ifdef SOCKET_SEND_COW
#include <vm/vm_object.h>
#endif
@@ -66,7 +66,7 @@ SYSCTL_INT(_kern, KERN_IOV_MAX, iov_max,
static int uiomove_faultflag(void *cp, int n, struct uio *uio, int nofault);
-#ifdef ZERO_COPY_SOCKETS
+#ifdef SOCKET_SEND_COW
/* Declared in uipc_socket.c */
extern int so_zero_copy_receive;
@@ -128,7 +128,7 @@ retry:
vm_map_lookup_done(map, entry);
return(KERN_SUCCESS);
}
-#endif /* ZERO_COPY_SOCKETS */
+#endif /* SOCKET_SEND_COW */
int
copyin_nofault(const void *udaddr, void *kaddr, size_t len)
@@ -261,7 +261,7 @@ uiomove_frombuf(void *buf, int buflen, s
return (uiomove((char *)buf + offset, n, uio));
}
-#ifdef ZERO_COPY_SOCKETS
+#ifdef SOCKET_RECV_PFLIP
/*
* Experimental support for zero-copy I/O
*/
@@ -356,7 +356,7 @@ uiomoveco(void *cp, int n, struct uio *u
}
return (0);
}
-#endif /* ZERO_COPY_SOCKETS */
+#endif /* SOCKET_RECV_PFLIP */
/*
* Give next character to user as result of read.
Modified: head/sys/kern/uipc_socket.c
==============================================================================
--- head/sys/kern/uipc_socket.c Tue Oct 23 12:39:17 2012 (r241930)
+++ head/sys/kern/uipc_socket.c Tue Oct 23 14:19:44 2012 (r241931)
@@ -219,17 +219,20 @@ static int numopensockets;
SYSCTL_INT(_kern_ipc, OID_AUTO, numopensockets, CTLFLAG_RD,
&numopensockets, 0, "Number of open sockets");
-#ifdef ZERO_COPY_SOCKETS
-/* These aren't static because they're used in other files. */
-int so_zero_copy_send = 1;
-int so_zero_copy_receive = 1;
+#if defined(SOCKET_SEND_COW) || defined(SOCKET_RECV_PFLIP)
SYSCTL_NODE(_kern_ipc, OID_AUTO, zero_copy, CTLFLAG_RD, 0,
"Zero copy controls");
+#ifdef SOCKET_RECV_PFLIP
+int so_zero_copy_receive = 1;
SYSCTL_INT(_kern_ipc_zero_copy, OID_AUTO, receive, CTLFLAG_RW,
&so_zero_copy_receive, 0, "Enable zero copy receive");
+#endif
+#ifdef SOCKET_SEND_COW
+int so_zero_copy_send = 1;
SYSCTL_INT(_kern_ipc_zero_copy, OID_AUTO, send, CTLFLAG_RW,
&so_zero_copy_send, 0, "Enable zero copy send");
-#endif /* ZERO_COPY_SOCKETS */
+#endif /* SOCKET_SEND_COW */
+#endif /* SOCKET_SEND_COW || SOCKET_RECV_PFLIP */
/*
* accept_mtx locks down per-socket fields relating to accept queues. See
@@ -903,7 +906,7 @@ sodisconnect(struct socket *so)
return (error);
}
-#ifdef ZERO_COPY_SOCKETS
+#ifdef SOCKET_SEND_COW
struct so_zerocopy_stats{
int size_ok;
int align_ok;
@@ -1008,7 +1011,7 @@ out:
*retmp = top;
return (error);
}
-#endif /* ZERO_COPY_SOCKETS */
+#endif /* SOCKET_SEND_COW */
#define SBLOCKWAIT(f) (((f) & MSG_DONTWAIT) ? 0 : SBL_WAIT)
@@ -1019,7 +1022,7 @@ sosend_dgram(struct socket *so, struct s
long space;
ssize_t resid;
int clen = 0, error, dontroute;
-#ifdef ZERO_COPY_SOCKETS
+#ifdef SOCKET_SEND_COW
int atomic = sosendallatonce(so) || top;
#endif
@@ -1104,7 +1107,7 @@ sosend_dgram(struct socket *so, struct s
if (flags & MSG_EOR)
top->m_flags |= M_EOR;
} else {
-#ifdef ZERO_COPY_SOCKETS
+#ifdef SOCKET_SEND_COW
error = sosend_copyin(uio, &top, atomic, &space, flags);
if (error)
goto out;
@@ -1121,7 +1124,7 @@ sosend_dgram(struct socket *so, struct s
goto out;
}
space -= resid - uio->uio_resid;
-#endif
+#endif /* SOCKET_SEND_COW */
resid = uio->uio_resid;
}
KASSERT(resid == 0, ("sosend_dgram: resid != 0"));
@@ -1293,7 +1296,7 @@ restart:
if (flags & MSG_EOR)
top->m_flags |= M_EOR;
} else {
-#ifdef ZERO_COPY_SOCKETS
+#ifdef SOCKET_SEND_COW
error = sosend_copyin(uio, &top, atomic,
&space, flags);
if (error != 0)
@@ -1313,7 +1316,7 @@ restart:
goto release;
}
space -= resid - uio->uio_resid;
-#endif
+#endif /* SOCKET_SEND_COW */
resid = uio->uio_resid;
}
if (dontroute) {
@@ -1405,7 +1408,7 @@ soreceive_rcvoob(struct socket *so, stru
if (error)
goto bad;
do {
-#ifdef ZERO_COPY_SOCKETS
+#ifdef SOCKET_RECV_PFLIP
if (so_zero_copy_receive) {
int disposable;
@@ -1419,7 +1422,7 @@ soreceive_rcvoob(struct socket *so, stru
min(uio->uio_resid, m->m_len),
uio, disposable);
} else
-#endif /* ZERO_COPY_SOCKETS */
+#endif /* SOCKET_RECV_PFLIP */
error = uiomove(mtod(m, void *),
(int) min(uio->uio_resid, m->m_len), uio);
m = m_free(m);
@@ -1743,7 +1746,7 @@ dontblock:
SBLASTRECORDCHK(&so->so_rcv);
SBLASTMBUFCHK(&so->so_rcv);
SOCKBUF_UNLOCK(&so->so_rcv);
-#ifdef ZERO_COPY_SOCKETS
+#ifdef SOCKET_RECV_PFLIP
if (so_zero_copy_receive) {
int disposable;
@@ -1757,7 +1760,7 @@ dontblock:
(int)len, uio,
disposable);
} else
-#endif /* ZERO_COPY_SOCKETS */
+#endif /* SOCKET_RECV_PFLIP */
error = uiomove(mtod(m, char *) + moff, (int)len, uio);
SOCKBUF_LOCK(&so->so_rcv);
if (error) {
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