bus: add benchmark tool to determine the right threshold for copying vs. memfd

.gitignore

@@ -84,6 +84,7 @@
 /test-bus-chat
 /test-bus-kernel
 /test-bus-kernel-bloom
+/test-bus-kernel-benchmark
 /test-bus-marshal
 /test-bus-match
 /test-bus-memfd

Makefile.am

@@ -1764,6 +1764,7 @@ tests += \
 	test-bus-match \
 	test-bus-kernel \
 	test-bus-kernel-bloom \
+	test-bus-kernel-benchmark \
 	test-bus-memfd \
 	test-bus-zero-copy
 
@@ -1848,6 +1849,17 @@ test_bus_kernel_bloom_LDADD = \
 	libsystemd-bus.la \
 	libsystemd-id128-internal.la
 
+test_bus_kernel_benchmark_SOURCES = \
+	src/libsystemd-bus/test-bus-kernel-benchmark.c
+
+test_bus_kernel_benchmark_CFLAGS = \
+	$(AM_CFLAGS)
+
+test_bus_kernel_benchmark_LDADD = \
+	libsystemd-shared.la \
+	libsystemd-bus.la \
+	libsystemd-id128-internal.la
+
 test_bus_memfd_SOURCES = \
 	src/libsystemd-bus/test-bus-memfd.c
 

src/libsystemd-bus/bus-internal.h

@@ -111,6 +111,8 @@ struct sd_bus {
         bool filter_callbacks_modified:1;
         bool object_callbacks_modified:1;
 
+        int use_memfd;
+
         void *rbuffer;
         size_t rbuffer_size;
 

src/libsystemd-bus/bus-kernel.c

@@ -326,6 +326,8 @@ int bus_kernel_take_fd(sd_bus *b) {
         if (b->is_server)
                 return -EINVAL;
 
+        b->use_memfd = 1;
+
         if (!b->kdbus_buffer) {
                 b->kdbus_buffer = mmap(NULL, KDBUS_POOL_SIZE, PROT_READ|PROT_WRITE, MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
                 if (b->kdbus_buffer == MAP_FAILED) {

src/libsystemd-bus/bus-message.c

@@ -564,7 +564,7 @@ static int message_new_reply(
                 goto fail;
 
         if (call->sender) {
-                r = message_append_field_string(t, SD_BUS_MESSAGE_HEADER_DESTINATION, SD_BUS_TYPE_STRING, call->sender, &t->sender);
+                r = message_append_field_string(t, SD_BUS_MESSAGE_HEADER_DESTINATION, SD_BUS_TYPE_STRING, call->sender, &t->destination);
                 if (r < 0)
                         goto fail;
         }
@@ -3865,9 +3865,9 @@ int bus_message_seal(sd_bus_message *m, uint64_t serial) {
         /* If this is something we can send as memfd, then let's seal
         the memfd now. Note that we can send memfds as payload only
         for directed messages, and not for broadcasts. */
-        if (m->destination) {
+        if (m->destination && m->bus && m->bus->use_memfd) {
                 MESSAGE_FOREACH_PART(part, i, m)
-                        if (part->memfd >= 0 && !part->sealed && part->size > MEMFD_MIN_SIZE) {
+                        if (part->memfd >= 0 && !part->sealed && (part->size > MEMFD_MIN_SIZE || m->bus->use_memfd < 0)) {
                                 bus_body_part_unmap(part);
 
                                 if (ioctl(part->memfd, KDBUS_CMD_MEMFD_SEAL_SET, 1) >= 0)

src/libsystemd-bus/sd-bus.c

@@ -2514,6 +2514,7 @@ int sd_bus_call_method(
         int r;
 
         if (!bus)
+
                 return -EINVAL;
         if (!BUS_IS_OPEN(bus->state))
                 return -ENOTCONN;

src/libsystemd-bus/test-bus-kernel-benchmark.c

@@ -0,0 +1,225 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2013 Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <ctype.h>
+#include <sys/wait.h>
+
+#include "util.h"
+#include "log.h"
+
+#include "sd-bus.h"
+#include "bus-message.h"
+#include "bus-error.h"
+#include "bus-kernel.h"
+#include "bus-internal.h"
+
+#define N_TRIES 500
+#define MAX_SIZE (5*1024*1024)
+
+static void server(sd_bus *b, usec_t *result) {
+        usec_t x = 0;
+        int r;
+
+        for (;;) {
+                _cleanup_bus_message_unref_ sd_bus_message *m = NULL;
+
+                r = sd_bus_process(b, &m);
+                assert_se(r >= 0);
+
+                if (r == 0)
+                        assert_se(sd_bus_wait(b, (usec_t) -1) >= 0);
+
+                if (!m)
+                        continue;
+
+                /* log_error("huhu %s from %s", sd_bus_message_get_member(m), sd_bus_message_get_sender(m)); */
+
+                if (sd_bus_message_is_method_call(m, "benchmark.server", "Work")) {
+                        _cleanup_bus_message_unref_ sd_bus_message *reply = NULL;
+                        size_t i, sz;
+                        char *q;
+                        const char *p;
+
+                        assert_se(sd_bus_message_read_array(m, 'y', (const void**) &p, &sz) > 0);
+                        assert_se(sd_bus_message_new_method_return(b, m, &reply) >= 0);
+                        assert_se(sd_bus_message_append_array_space(reply, 'y', sz, (void**) &q) >= 0);
+
+                        x = now(CLOCK_MONOTONIC);
+
+                        for (i = 0; i < sz; i++)
+                                q[i] = toupper(p[i]);
+
+                        x = now(CLOCK_MONOTONIC) - x;
+
+                        assert_se(sd_bus_send(b, reply, NULL) >= 0);
+                } else if (sd_bus_message_is_method_call(m, "benchmark.server", "Exit")) {
+                        usec_t t;
+
+                        assert_se(sd_bus_message_read(m, "t", &t) > 0);
+                        assert_se(t >= x);
+                        *result = t - x;
+                        return;
+
+                } else if (sd_bus_message_is_method_call(m, "benchmark.server", "Ping")) {
+                        assert_se(sd_bus_reply_method_return(b, m, "y", 1) >= 0);
+                } else
+                        assert_not_reached("Unknown method");
+        }
+}
+
+static void client(sd_bus *b, size_t sz) {
+        _cleanup_bus_message_unref_ sd_bus_message *m = NULL, *reply = NULL;
+        char *p;
+        const char *q;
+        usec_t t;
+        size_t l, i;
+
+        assert_se(sd_bus_call_method(b, ":1.1", "/", "benchmark.server", "Ping", NULL, NULL, NULL) >= 0);
+
+        assert_se(sd_bus_message_new_method_call(b, ":1.1", "/", "benchmark.server", "Work", &m) >= 0);
+        assert_se(sd_bus_message_append_array_space(m, 'y', sz, (void**) &p) >= 0);
+
+        for (i = 0; i < sz; i++)
+                p[i] = 'a' + (char) (i % 26);
+
+        t = now(CLOCK_MONOTONIC);
+        assert_se(sd_bus_send_with_reply_and_block(b, m, 0, NULL, &reply) >= 0);
+        t = now(CLOCK_MONOTONIC) - t;
+
+        assert_se(sd_bus_message_read_array(reply, 'y', (const void**) &q, &l) > 0);
+        assert_se(l == sz);
+
+        for (i = 0; i < sz; i++) {
+                assert_se(q[i] == 'A' + (char) (i % 26));
+        }
+
+        sd_bus_message_unref(m);
+
+        assert_se(sd_bus_message_new_method_call(b, ":1.1", "/", "benchmark.server", "Exit", &m) >= 0);
+        assert_se(sd_bus_message_append(m, "t", t) >= 0);
+        assert_se(sd_bus_send(b, m, NULL) >= 0);
+}
+
+static void run_benchmark(size_t sz, bool force_copy, usec_t *result) {
+
+        _cleanup_close_ int bus_ref = -1;
+        _cleanup_free_ char *bus_name = NULL, *address = NULL;
+        sd_bus *b;
+        int r;
+        pid_t pid;
+
+        bus_ref = bus_kernel_create("deine-mutter", &bus_name);
+        if (bus_ref == -ENOENT)
+                exit(EXIT_TEST_SKIP);
+
+        assert_se(bus_ref >= 0);
+
+        address = strappend("kernel:path=", bus_name);
+        assert_se(address);
+
+        r = sd_bus_new(&b);
+        assert_se(r >= 0);
+
+        b->use_memfd = force_copy ? 0 : -1;
+
+        r = sd_bus_set_address(b, address);
+        assert_se(r >= 0);
+
+        r = sd_bus_start(b);
+        assert_se(r >= 0);
+
+        pid = fork();
+        assert_se(pid >= 0);
+
+        if (pid == 0) {
+                close_nointr_nofail(bus_ref);
+                sd_bus_unref(b);
+
+                r = sd_bus_new(&b);
+                assert_se(r >= 0);
+
+                b->use_memfd = force_copy ? 0 : -1;
+
+                r = sd_bus_set_address(b, address);
+                assert_se(r >= 0);
+
+                r = sd_bus_start(b);
+                assert_se(r >= 0);
+
+                client(b, sz);
+                _exit(0);
+        }
+
+        server(b, result);
+        sd_bus_unref(b);
+
+        assert_se(waitpid(pid, NULL, 0) == pid);
+}
+
+int main(int argc, char *argv[]) {
+        size_t lsize, rsize, csize;
+
+        log_set_max_level(LOG_DEBUG);
+
+        lsize = 1;
+        rsize = MAX_SIZE;
+
+        for (;;) {
+                usec_t copy = 0, memfd = 0;
+                unsigned i;
+
+                csize = (lsize + rsize) / 2;
+
+                log_info("Trying size=%zu", csize);
+
+                if (csize <= lsize)
+                        break;
+
+                for (i = 0; i <  N_TRIES; i++) {
+                        usec_t t;
+
+                        run_benchmark(csize, true, &t);
+                        copy += t;
+                }
+
+                for (i = 0; i < N_TRIES; i++) {
+                        usec_t t;
+
+                        run_benchmark(csize, false, &t);
+                        memfd += t;
+                }
+
+                copy /= N_TRIES;
+                memfd /= N_TRIES;
+
+                if (copy == memfd)
+                        break;
+
+                if (copy < memfd)
+                        lsize = csize;
+                else
+                        rsize = csize;
+        }
+
+        log_info("Copying/memfd are equally fast at %zu", csize);
+
+        return 0;
+}