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Date: Tue, 24 Sep 2002 00:05:39 +1000
From: Rusty Russell <rusty@rustcorp.com.au>
To: Andrew Morton <akpm@digeo.com>
Cc: phillips@arcor.de, ciarrocchi@linuxmail.org, linux-kernel@vger.kernel.org,
       mingo@redhat.com
Subject: Re: [chatroom benchmark version 1.0.1] Results
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On Thu, 19 Sep 2002 01:29:30 -0700
Andrew Morton <akpm@digeo.com> wrote:

> Daniel Phillips wrote:
> > 
> > Just thought I'd bounce this one over to Andrew as a warm-n-fuzzy.
> 
> Is a scheduler test, isn't it?

Mixed.  Before the O(1) scheduler, I distilled this test into "hackbench"
(which I now call schedbench).  Do well on this, and you'll do well on the
lots-of-threads-wakingup case: [BTW, 2.5 rocks at this 8)].  Ideally
"hackbench n" should scale with n:

/* Test groups of 20 processes spraying to 20 receivers */
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <sys/time.h>
#include <sys/select.h>

#define DATASIZE 100
static unsigned int loops = 100;
static int use_pipes = 0;

static void barf(const char *msg)
{
	fprintf(stderr, "%s (error: %s)\n", msg, strerror(errno));
	exit(1);
}

static void fdpair(int fds[2])
{
	if (use_pipes) {
		if (pipe(fds) == 0)
			return;
	} else {
		if (socketpair(AF_UNIX, SOCK_STREAM, 0, fds) == 0)
			return;
	}
	barf("Creating fdpair");
}

/* Block until we're ready to go */
static void ready(int ready_out, int wakefd)
{
	char dummy;
	fd_set fds;

	FD_ZERO(&fds);
	FD_SET(wakefd, &fds);

	/* Tell them we're ready. */
	if (write(ready_out, &dummy, 1) != 1)
		barf("CLIENT: ready write");

	/* Wait for "GO" signal */
	if (select(wakefd+1, &fds, NULL, NULL, NULL) != 1)
		barf("select");
}

/* Sender sprays loops messages down each file descriptor */
static void sender(unsigned int num_fds,
		   int out_fd[num_fds],
		   int ready_out,
		   int wakefd)
{
	char data[DATASIZE];
	unsigned int i, j;

	ready(ready_out, wakefd);

	/* Now pump to every receiver. */
	for (i = 0; i < loops; i++) {
		for (j = 0; j < num_fds; j++) {
			int ret, done = 0;

		again:
			ret = write(out_fd[j], data + done, sizeof(data)-done);
			if (ret < 0)
				barf("SENDER: write");
			done += ret;
			if (done < sizeof(data))
				goto again;
		}
	}
}

/* One receiver per fd */
static void receiver(unsigned int num_packets,
		     int in_fd,
		     int ready_out,
		     int wakefd)
{
	unsigned int i;

	/* Wait for start... */
	ready(ready_out, wakefd);

	/* Receive them all */
	for (i = 0; i < num_packets; i++) {
		char data[DATASIZE];
		int ret, done = 0;

	again:
		ret = read(in_fd, data + done, DATASIZE - done);
		if (ret < 0)
			barf("SERVER: read");
		done += ret;
		if (done < DATASIZE)
			goto again;
	}
}

/* One group of senders and receivers */
static unsigned int group(unsigned int num_fds,
			  int ready_out,
			  int wakefd)
{
	unsigned int i;
	unsigned int out_fds[num_fds];

	for (i = 0; i < num_fds; i++) {
		int fds[2];

		/* Create the pipe between client and server */
		fdpair(fds);

		/* Fork the receiver. */
		switch (fork()) {
		case -1: barf("fork()");
		case 0:
			close(fds[1]);
			receiver(num_fds*loops, fds[0], ready_out, wakefd);
			exit(0);
		}

		out_fds[i] = fds[1];
		close(fds[0]);
	}

	/* Now we have all the fds, fork the senders */
	for (i = 0; i < num_fds; i++) {
		switch (fork()) {
		case -1: barf("fork()");
		case 0:
			sender(num_fds, out_fds, ready_out, wakefd);
			exit(0);
		}
	}

	/* Close the fds we have left */
	for (i = 0; i < num_fds; i++)
		close(out_fds[i]);

	/* Return number of children to reap */
	return num_fds * 2;
}

int main(int argc, char *argv[])
{
	unsigned int i, num_groups, total_children;
	struct timeval start, stop, diff;
	unsigned int num_fds = 20;
	int readyfds[2], wakefds[2];
	char dummy;

	if (argv[1] && strcmp(argv[1], "-pipe") == 0) {
		use_pipes = 1;
		argc--;
		argv++;
	}

	if (argc != 2 || (num_groups = atoi(argv[1])) == 0)
		barf("Usage: hackbench [-pipe] <num groups>\n");

	fdpair(readyfds);
	fdpair(wakefds);

	total_children = 0;
	for (i = 0; i < num_groups; i++)
		total_children += group(num_fds, readyfds[1], wakefds[0]);

	/* Wait for everyone to be ready */
	for (i = 0; i < total_children; i++)
		if (read(readyfds[0], &dummy, 1) != 1)
			barf("Reading for readyfds");

	gettimeofday(&start, NULL);

	/* Kick them off */
	if (write(wakefds[1], &dummy, 1) != 1)
		barf("Writing to start them");

	/* Reap them all */
	for (i = 0; i < total_children; i++) {
		int status;
		wait(&status);
		if (!WIFEXITED(status))
			exit(1);
	}

	gettimeofday(&stop, NULL);

	/* Print time... */
	timersub(&stop, &start, &diff);
	printf("Time: %lu.%03lu\n", diff.tv_sec, diff.tv_usec/1000);
	exit(0);
}



-- 
   there are those who do and those who hang on and you don't see too
   many doers quoting their contemporaries.  -- Larry McVoy
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