tools/virtio: add ringtest utilities

This adds micro-benchmarks useful for tuning virtio ring layouts.
Three layouts are currently implemented:

- virtio 0.9 compatible one
- an experimental extension bypassing the ring index, polling ring
  itself instead
- an experimental extension bypassing avail and used ring completely

Typical use:

sh run-on-all.sh perf stat -r 10 --log-fd 1 -- ./ring

It doesn't depend on the kernel directly, but it's handy
to have as much virtio stuff as possible in one tree.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

tools/virtio/ringtest/Makefile

@@ -0,0 +1,22 @@
+all:
+
+all: ring virtio_ring_0_9 virtio_ring_poll
+
+CFLAGS += -Wall
+CFLAGS += -pthread -O2 -ggdb
+LDFLAGS += -pthread -O2 -ggdb
+
+main.o: main.c main.h
+ring.o: ring.c main.h
+virtio_ring_0_9.o: virtio_ring_0_9.c main.h
+virtio_ring_poll.o: virtio_ring_poll.c virtio_ring_0_9.c main.h
+ring: ring.o main.o
+virtio_ring_0_9: virtio_ring_0_9.o main.o
+virtio_ring_poll: virtio_ring_poll.o main.o
+clean:
+	-rm main.o
+	-rm ring.o ring
+	-rm virtio_ring_0_9.o virtio_ring_0_9
+	-rm virtio_ring_poll.o virtio_ring_poll
+
+.PHONY: all clean

tools/virtio/ringtest/README

@@ -0,0 +1,2 @@
+Partial implementation of various ring layouts, useful to tune virtio design.
+Uses shared memory heavily.

tools/virtio/ringtest/main.c

@@ -0,0 +1,366 @@
+/*
+ * Copyright (C) 2016 Red Hat, Inc.
+ * Author: Michael S. Tsirkin <mst@redhat.com>
+ * This work is licensed under the terms of the GNU GPL, version 2.
+ *
+ * Command line processing and common functions for ring benchmarking.
+ */
+#define _GNU_SOURCE
+#include <getopt.h>
+#include <pthread.h>
+#include <assert.h>
+#include <sched.h>
+#include "main.h"
+#include <sys/eventfd.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <limits.h>
+
+int runcycles = 10000000;
+int max_outstanding = INT_MAX;
+int batch = 1;
+
+bool do_sleep = false;
+bool do_relax = false;
+bool do_exit = true;
+
+unsigned ring_size = 256;
+
+static int kickfd = -1;
+static int callfd = -1;
+
+void notify(int fd)
+{
+	unsigned long long v = 1;
+	int r;
+
+	vmexit();
+	r = write(fd, &v, sizeof v);
+	assert(r == sizeof v);
+	vmentry();
+}
+
+void wait_for_notify(int fd)
+{
+	unsigned long long v = 1;
+	int r;
+
+	vmexit();
+	r = read(fd, &v, sizeof v);
+	assert(r == sizeof v);
+	vmentry();
+}
+
+void kick(void)
+{
+	notify(kickfd);
+}
+
+void wait_for_kick(void)
+{
+	wait_for_notify(kickfd);
+}
+
+void call(void)
+{
+	notify(callfd);
+}
+
+void wait_for_call(void)
+{
+	wait_for_notify(callfd);
+}
+
+void set_affinity(const char *arg)
+{
+	cpu_set_t cpuset;
+	int ret;
+	pthread_t self;
+	long int cpu;
+	char *endptr;
+
+	if (!arg)
+		return;
+
+	cpu = strtol(arg, &endptr, 0);
+	assert(!*endptr);
+
+	assert(cpu >= 0 || cpu < CPU_SETSIZE);
+
+	self = pthread_self();
+	CPU_ZERO(&cpuset);
+	CPU_SET(cpu, &cpuset);
+
+	ret = pthread_setaffinity_np(self, sizeof(cpu_set_t), &cpuset);
+	assert(!ret);
+}
+
+static void run_guest(void)
+{
+	int completed_before;
+	int completed = 0;
+	int started = 0;
+	int bufs = runcycles;
+	int spurious = 0;
+	int r;
+	unsigned len;
+	void *buf;
+	int tokick = batch;
+
+	for (;;) {
+		if (do_sleep)
+			disable_call();
+		completed_before = completed;
+		do {
+			if (started < bufs &&
+			    started - completed < max_outstanding) {
+				r = add_inbuf(0, NULL, "Hello, world!");
+				if (__builtin_expect(r == 0, true)) {
+					++started;
+					if (!--tokick) {
+						tokick = batch;
+						if (do_sleep)
+							kick_available();
+					}
+
+				}
+			} else
+				r = -1;
+
+			/* Flush out completed bufs if any */
+			if (get_buf(&len, &buf)) {
+				++completed;
+				if (__builtin_expect(completed == bufs, false))
+					return;
+				r = 0;
+			}
+		} while (r == 0);
+		if (completed == completed_before)
+			++spurious;
+		assert(completed <= bufs);
+		assert(started <= bufs);
+		if (do_sleep) {
+			if (enable_call())
+				wait_for_call();
+		} else {
+			poll_used();
+		}
+	}
+}
+
+static void run_host(void)
+{
+	int completed_before;
+	int completed = 0;
+	int spurious = 0;
+	int bufs = runcycles;
+	unsigned len;
+	void *buf;
+
+	for (;;) {
+		if (do_sleep) {
+			if (enable_kick())
+				wait_for_kick();
+		} else {
+			poll_avail();
+		}
+		if (do_sleep)
+			disable_kick();
+		completed_before = completed;
+		while (__builtin_expect(use_buf(&len, &buf), true)) {
+			if (do_sleep)
+				call_used();
+			++completed;
+			if (__builtin_expect(completed == bufs, false))
+				return;
+		}
+		if (completed == completed_before)
+			++spurious;
+		assert(completed <= bufs);
+		if (completed == bufs)
+			break;
+	}
+}
+
+void *start_guest(void *arg)
+{
+	set_affinity(arg);
+	run_guest();
+	pthread_exit(NULL);
+}
+
+void *start_host(void *arg)
+{
+	set_affinity(arg);
+	run_host();
+	pthread_exit(NULL);
+}
+
+static const char optstring[] = "";
+static const struct option longopts[] = {
+	{
+		.name = "help",
+		.has_arg = no_argument,
+		.val = 'h',
+	},
+	{
+		.name = "host-affinity",
+		.has_arg = required_argument,
+		.val = 'H',
+	},
+	{
+		.name = "guest-affinity",
+		.has_arg = required_argument,
+		.val = 'G',
+	},
+	{
+		.name = "ring-size",
+		.has_arg = required_argument,
+		.val = 'R',
+	},
+	{
+		.name = "run-cycles",
+		.has_arg = required_argument,
+		.val = 'C',
+	},
+	{
+		.name = "outstanding",
+		.has_arg = required_argument,
+		.val = 'o',
+	},
+	{
+		.name = "batch",
+		.has_arg = required_argument,
+		.val = 'b',
+	},
+	{
+		.name = "sleep",
+		.has_arg = no_argument,
+		.val = 's',
+	},
+	{
+		.name = "relax",
+		.has_arg = no_argument,
+		.val = 'x',
+	},
+	{
+		.name = "exit",
+		.has_arg = no_argument,
+		.val = 'e',
+	},
+	{
+	}
+};
+
+static void help(void)
+{
+	fprintf(stderr, "Usage: <test> [--help]"
+		" [--host-affinity H]"
+		" [--guest-affinity G]"
+		" [--ring-size R (default: %d)]"
+		" [--run-cycles C (default: %d)]"
+		" [--batch b]"
+		" [--outstanding o]"
+		" [--sleep]"
+		" [--relax]"
+		" [--exit]"
+		"\n",
+		ring_size,
+		runcycles);
+}
+
+int main(int argc, char **argv)
+{
+	int ret;
+	pthread_t host, guest;
+	void *tret;
+	char *host_arg = NULL;
+	char *guest_arg = NULL;
+	char *endptr;
+	long int c;
+
+	kickfd = eventfd(0, 0);
+	assert(kickfd >= 0);
+	callfd = eventfd(0, 0);
+	assert(callfd >= 0);
+
+	for (;;) {
+		int o = getopt_long(argc, argv, optstring, longopts, NULL);
+		switch (o) {
+		case -1:
+			goto done;
+		case '?':
+			help();
+			exit(2);
+		case 'H':
+			host_arg = optarg;
+			break;
+		case 'G':
+			guest_arg = optarg;
+			break;
+		case 'R':
+			ring_size = strtol(optarg, &endptr, 0);
+			assert(ring_size && !(ring_size & (ring_size - 1)));
+			assert(!*endptr);
+			break;
+		case 'C':
+			c = strtol(optarg, &endptr, 0);
+			assert(!*endptr);
+			assert(c > 0 && c < INT_MAX);
+			runcycles = c;
+			break;
+		case 'o':
+			c = strtol(optarg, &endptr, 0);
+			assert(!*endptr);
+			assert(c > 0 && c < INT_MAX);
+			max_outstanding = c;
+			break;
+		case 'b':
+			c = strtol(optarg, &endptr, 0);
+			assert(!*endptr);
+			assert(c > 0 && c < INT_MAX);
+			batch = c;
+			break;
+		case 's':
+			do_sleep = true;
+			break;
+		case 'x':
+			do_relax = true;
+			break;
+		case 'e':
+			do_exit = true;
+			break;
+		default:
+			help();
+			exit(4);
+			break;
+		}
+	}
+
+	/* does nothing here, used to make sure all smp APIs compile */
+	smp_acquire();
+	smp_release();
+	smp_mb();
+done:
+
+	if (batch > max_outstanding)
+		batch = max_outstanding;
+
+	if (optind < argc) {
+		help();
+		exit(4);
+	}
+	alloc_ring();
+
+	ret = pthread_create(&host, NULL, start_host, host_arg);
+	assert(!ret);
+	ret = pthread_create(&guest, NULL, start_guest, guest_arg);
+	assert(!ret);
+
+	ret = pthread_join(guest, &tret);
+	assert(!ret);
+	ret = pthread_join(host, &tret);
+	assert(!ret);
+	return 0;
+}