mybw: Quick hack to measure memory read performance

Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

.gitignore

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+mybw
+*.o

Makefile

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+OUT := mybw
+
+CFLAGS := -O2 -Wall -fno-builtin
+LDFLAGS := -static -static-libgcc
+
+SRCS := mybw.c
+OBJS := $(SRCS:.c=.o)
+
+$(OUT): $(OBJS)
+	$(CC) -o $@ $^ $(LDFLAGS)
+
+clean:
+	rm -f $(OUT) $(OBJS)

mybw.c

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+/*
+ * Copyright (c) 2022, Linaro Ltd.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ * this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ * this list of conditions and the following disclaimer in the documentation
+ * and/or other materials provided with the distribution.
+ *
+ * 3. Neither the name of the copyright holder nor the names of its contributors
+ * may be used to endorse or promote products derived from this software without
+ * specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/* gcc -O2 -Wall -fno-builtin -o mybw mybw.c */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+#include <time.h>
+
+#define NSEC_PER_SEC 1000000000UL
+
+#define TEST_SIZE (50 * 1024ULL*1024*1024) /* 50G */
+
+static char *sizestr(uint64_t sz)
+{
+	static char str[16];
+
+	if (sz > 1024 * 1024)
+		snprintf(str, sizeof(str), "%5luM", sz / (1024*1024));
+	else if (sz > 1024)
+		snprintf(str, sizeof(str), "%5luK", sz / 1024);
+	else
+		snprintf(str, sizeof(str), "%6lu", sz);
+
+	return str;
+}
+
+static void measure(uint64_t block_size)
+{
+	struct timespec start;
+	struct timespec end;
+	uint64_t block;
+	uint64_t ts;
+	void *source;
+	void *sink;
+
+	if (block_size > TEST_SIZE)
+		return;
+
+	sink = malloc(block_size);
+	memset(sink, 0, block_size);
+
+	source = malloc(block_size);
+	memset(source, 0xcd, block_size);
+
+	clock_gettime(CLOCK_MONOTONIC, &start);
+
+	for (block = 0; block < (TEST_SIZE / block_size); block++)
+		memcpy(sink, source, block_size);
+
+	clock_gettime(CLOCK_MONOTONIC, &end);
+
+	free(sink);
+	free(source);
+
+	ts = ((end.tv_sec - start.tv_sec) * NSEC_PER_SEC) + (end.tv_nsec - start.tv_nsec);
+
+	printf("%s: %.02fMB/s\n", sizestr(block_size), (double)TEST_SIZE * 1000 / ts);
+}
+
+int main()
+{
+	int i;
+
+	for (i = 64; i <= 32 * 1024 * 1024; i <<= 1)
+		measure(i);
+
+	return 0;
+}