Date: Sun, 14 Feb 1999 12:08:16 -0800 (PST) From: Matthew Dillon <dillon@apollo.backplane.com> To: freebsd-current@FreeBSD.ORG Subject: Weird piecemeal reads over socketpair() pipe breaks up small writes into even smaller reads. Message-ID: <199902142008.MAA07550@apollo.backplane.com>
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This is under -current. I don't know when it started, but I think whatever
change is causing this was in the last week or two.
This isn't a 'bug', per say, but it bothers me that a small 128 byte
write() is being somehow broken apart into two smaller read()s. It isn't
efficient, and it shouldn't be happening.
-Matt
Matthew Dillon
<dillon@backplane.com>
apollo:/home/dillon> ./x
read 96
read 32
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h> /* unix domain sockets */
#include <netinet/in.h> /* internet sockets */
#include <netinet/tcp.h> /* TCP_NODELAY sockopt */
#include <stdio.h>
#include <fcntl.h>
int
main(int ac, char **av)
{
int fds[2];
int n;
char buf[128];
fd_set rfds;
if (socketpair(PF_UNIX, SOCK_STREAM, IPPROTO_IP, fds) < 0)
perror("socketpair");
fcntl(fds[0], F_SETFL, O_NONBLOCK);
FD_ZERO(&rfds);
FD_SET(fds[0], &rfds);
if (fork() == 0) {
sleep(1);
write(fds[1], buf, sizeof(buf));
_exit(1);
}
select(fds[0] + 1, &rfds, NULL, NULL, NULL);
while ((n = read(fds[0], buf, sizeof(buf))) > 0)
printf("read %d\n", n);
return(0);
}
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