I am using the splice syscall in kernel 2.6.25.4 with network socket
receive to splice incoming and outgoing TCP sockets. I perform something
like the following:
#define SPLICE_SIZE (12*1024)
int fd[2];
ret = pipe(fd);
ret = splice(src, NULL, fd[1], NULL, SPLICE_SIZE, SPLICE_F_MORE |
SPLICE_F_MOVE);
bytes_left = ret;
while (bytes_left > 0) {
ret = splice(fd[0], NULL, sink, NULL, bytes_left, SPLICE_F_NONBLOCK);
bytes_left -= ret;
}
This works well when SPLICE_SIZE is around 12K or lower, but anything
much more than that will cause the src splice call to block either right
away or after a few iterations. It almost seems as though the pipe
buffer is becoming full although I have used poll to check for both
sockets and pipe fds before calling splice, and the sink splice call
always sends the current number of bytes. I have also tried virtually
all combinations of the SPLICE_F_ options without success. Has anyone
run into a similar issue with socket-to-socket splicing and larger
splice sizes? I would really like to use the full 64K splice size to and
from the pipe.
I should mention that the splice test applications do work correctly
with 64K splice sizes when splicing to/from a network socket(s) to
STDOUT or STDIN. Any thoughts?
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