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faster path for TCP input

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Avoid polling a file descriptor to determine whether it has bytes;
just try to read, and then go to epoll/kevent mode when available,
skipping a poll/select.
This commit is contained in:
Matthew Flatt 2014-05-11 21:04:40 -06:00
parent 97da48ab67
commit 98b91a11e4
1 changed files with 50 additions and 56 deletions
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106
racket/src/racket/src/network.c
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@ -1321,36 +1321,61 @@ static intptr_t tcp_get_string(Scheme_Input_Port *port,
int errid;
int read_amt;
Scheme_Tcp *data;
Scheme_Object *sema;
data = (Scheme_Tcp *)port->port_data;
top:
while (1) {
if (scheme_unless_ready(unless))
return SCHEME_UNLESS_READY;
if (scheme_unless_ready(unless))
return SCHEME_UNLESS_READY;
if (port->closed) {
/* Another thread closed the input port while we were waiting. */
/* Call scheme_get_byte to signal the error */
scheme_get_byte((Scheme_Object *)port);
}
if (data->b.hiteof)
return EOF;
if (data->b.bufpos < data->b.bufmax) {
int n;
n = data->b.bufmax - data->b.bufpos;
n = ((size <= n)
? size
: n);
if (data->b.hiteof)
return EOF;
memcpy(buffer + offset, data->b.buffer + data->b.bufpos, n);
data->b.bufpos += n;
if (data->b.bufpos < data->b.bufmax) {
int n;
n = data->b.bufmax - data->b.bufpos;
n = ((size <= n)
? size
: n);
memcpy(buffer + offset, data->b.buffer + data->b.bufpos, n);
data->b.bufpos += n;
return n;
}
/* No data in buffer, so read from socket: */
if (!data->b.bufmode || (size > TCP_BUFFER_SIZE))
read_amt = TCP_BUFFER_SIZE;
else
read_amt = size;
return n;
}
while (!tcp_byte_ready(port, NULL)) {
if (nonblock > 0)
return 0;
{
Scheme_Object *sema;
int rn;
do {
rn = recv(data->tcp, data->b.buffer, read_amt, 0);
} while ((rn == -1) && (NOT_WINSOCK(errno) == EINTR));
data->b.bufmax = rn;
}
errid = SOCK_ERRNO();
if ((data->b.bufmax != -1) || !WAS_EAGAIN(errid)) {
/* got data or error */
break;
} else {
/* no data/error is immediately avaulable */
if (nonblock > 0)
return 0;
/* block until data is (probably) available */
sema = scheme_fd_to_semaphore(data->tcp, MZFD_CREATE_READ, 1);
if (sema)
scheme_wait_sema(sema, nonblock ? -1 : 0);
@ -1360,43 +1385,12 @@ static intptr_t tcp_get_string(Scheme_Input_Port *port,
(Scheme_Object *)port,
0.0, unless,
nonblock);
scheme_wait_input_allowed(port, nonblock);
}
scheme_wait_input_allowed(port, nonblock);
if (scheme_unless_ready(unless))
return SCHEME_UNLESS_READY;
}
if (port->closed) {
/* Another thread closed the input port while we were waiting. */
/* Call scheme_get_byte to signal the error */
scheme_get_byte((Scheme_Object *)port);
}
/* We assume that no other process has access to our sockets, so
when we unblock, there's definitely something to read. */
if (!data->b.bufmode || (size > TCP_BUFFER_SIZE))
read_amt = TCP_BUFFER_SIZE;
else
read_amt = size;
{
int rn;
do {
rn = recv(data->tcp, data->b.buffer, read_amt, 0);
} while ((rn == -1) && (NOT_WINSOCK(errno) == EINTR));
data->b.bufmax = rn;
}
errid = SOCK_ERRNO();
/* Is it possible that an EAGAIN error occurs? That means that data
isn't ready, even though select() says that data is ready. It
seems to happen for at least one user, and there appears to be
no harm in protecting against it. */
if ((data->b.bufmax == -1) && WAS_EAGAIN(errid))
goto top;
/* getting here means that data or error was ready */
if (data->b.bufmax == -1) {
scheme_raise_exn(MZEXN_FAIL_NETWORK,