From b3108c0bc1873ff72a3bbe694df07c7f3e7f1502 Mon Sep 17 00:00:00 2001
From: Tom Smeding <tom.smeding@gmail.com>
Date: Tue, 8 Oct 2019 16:44:13 +0200
Subject: Initial

---
 .gitignore  |  2 ++
 Makefile    | 13 ++++++++++++
 disk_perf.c | 68 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 83 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 Makefile
 create mode 100644 disk_perf.c

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..02a03ef
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+disk_perf
+
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..eca6140
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,13 @@
+CC = gcc
+CFLAGS = -Wall -Wextra -O3 -std=c99 -D_GNU_SOURCE
+BIN = disk_perf
+
+.PHONY: all clean
+
+all: $(BIN)
+
+$(BIN): disk_perf.c
+	$(CC) $(CFLAGS) -o $@ $<
+
+clean:
+	rm -f $(BIN)
diff --git a/disk_perf.c b/disk_perf.c
new file mode 100644
index 0000000..81c4095
--- /dev/null
+++ b/disk_perf.c
@@ -0,0 +1,68 @@
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <stdint.h>
+#include <assert.h>
+#include <sys/time.h>
+
+static uint64_t gettimestamp() {
+  struct timeval tv;
+  gettimeofday(&tv, NULL);
+  return tv.tv_sec * 1000000ULL + tv.tv_usec;
+}
+
+static void writeall(int fd, const void *buf, size_t count) {
+  size_t cursor = 0;
+  while (cursor < count) {
+    ssize_t written = write(fd, buf + cursor, count - cursor);
+    if (written < 0) {
+      perror("write");
+      exit(1);
+    }
+    assert(written > 0);
+    cursor += written;
+  }
+}
+
+int main(int argc, char **argv) {
+  if (argc != 2) {
+    fprintf(stderr, "Usage: %s <temp file to use>\n", argv[0]);
+    fprintf(stderr,
+        "This will write some data to a file as many times per second as\n"
+        "possible, calling fsync() after each write to make sure it is\n"
+        "persisted. This gives an upper bound on the number of ACID transactions\n"
+        "a single-threaded database can achieve on a disk.\n"
+		"The amount of data in one write is currently 18 bytes.\n"
+    );
+    return 1;
+  }
+
+  int fd = open(argv[1], O_WRONLY | O_CREAT, 0644);
+  if (fd < 0) {
+    perror("open");
+    return 1;
+  }
+
+  uint64_t start_stamp = gettimestamp();
+  size_t num_writes = 0;
+  for (size_t i = 0; ; i++) {
+    const char *str = "abcdefgh=01234567\n";
+    writeall(fd, str, strlen(str));
+    fsync(fd);
+    num_writes++;
+
+    if (i % 100 == 0) {
+      uint64_t now = gettimestamp();
+      double secs = (double)(now - start_stamp) / 1000000;
+      if (secs >= 4.0) {
+        printf("Speed: %zu writes in %lf seconds = %lf w/s\n",
+               num_writes, secs, num_writes / secs);
+
+        start_stamp = now;
+        num_writes = 0;
+      }
+    }
+  }
+}
-- 
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