From 785073f6589d0675d63b47064700134af33de947 Mon Sep 17 00:00:00 2001
From: David Sterba <dsterba@suse.com>
Date: Mon, 10 Jun 2019 14:49:50 +0200
Subject: [PATCH] btrfs-progs: crypto: add hash speedtest utility

A simple tool to microbenchmark performance of the hashes. Uses rdtsc
for timing, so works only on x86_64.

 $ make hash-speedtest
 $ ./hash-speedtest [iterations]

   Block size: 4096
   Iterations: 100000

       NULL-NOP: cycles:     56061823, c/i      560
    NULL-MEMCPY: cycles:     61296469, c/i      612
	 CRC32C: cycles:    179961796, c/i     1799
	 XXHASH: cycles:    138434590, c/i     1384

Signed-off-by: David Sterba <dsterba@suse.com>
---
 Makefile                |   4 ++
 crypto/hash-speedtest.c | 100 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 104 insertions(+)
 create mode 100644 crypto/hash-speedtest.c

diff --git a/Makefile b/Makefile
index fd99fb5c..37f47a28 100644
--- a/Makefile
+++ b/Makefile
@@ -646,6 +646,10 @@ fssum: tests/fssum.c crypto/sha224-256.c
 	@echo "    [LD]     $@"
 	$(Q)$(CC) $(CFLAGS) -o $@ $^ $(LDFLAGS)
 
+hash-speedtest: crypto/hash-speedtest.c $(objects) $(libs_static)
+	@echo "    [LD]     $@"
+	$(Q)$(CC) $(CFLAGS) -o $@ $^ $(LDFLAGS) $(LIBS)
+
 test-build: test-build-pre test-build-real
 
 test-build-pre:
diff --git a/crypto/hash-speedtest.c b/crypto/hash-speedtest.c
new file mode 100644
index 00000000..c3f6bbc8
--- /dev/null
+++ b/crypto/hash-speedtest.c
@@ -0,0 +1,100 @@
+#include "../kerncompat.h"
+#include "crypto/hash.h"
+#include "crypto/crc32c.h"
+
+#ifndef __x86_64__
+#error "Only x86_64 supported"
+#endif
+
+const int blocksize = 4096;
+int iterations = 100000;
+
+static __always_inline unsigned long long rdtsc(void)
+{
+	unsigned low, high;
+
+        asm volatile("rdtsc" : "=a" (low), "=d" (high));
+
+        return (low | ((u64)(high) << 32));
+}
+
+static inline u64 read_tsc(void)
+{
+       asm volatile("mfence");
+       return rdtsc();
+}
+
+/* Read the input and copy last bytes as the hash */
+static int hash_null_memcpy(const u8 *buf, size_t length, u8 *out)
+{
+       const u8 *end = buf + length;
+
+       while (buf + CRYPTO_HASH_SIZE_MAX < end) {
+               memcpy(out, buf, CRYPTO_HASH_SIZE_MAX);
+               buf += CRYPTO_HASH_SIZE_MAX;
+       }
+
+       return 0;
+}
+
+/* Test overhead of the calls */
+static int hash_null_nop(const u8 *buf, size_t length, u8 *out)
+{
+       memset(out, 0xFF, CRYPTO_HASH_SIZE_MAX);
+
+       return 0;
+}
+
+int main(int argc, char **argv) {
+	u8 buf[blocksize];
+	u8 hash[32];
+	int idx;
+	int iter;
+	struct contestant {
+		char name[16];
+		int (*digest)(const u8 *buf, size_t length, u8 *out);
+		int digest_size;
+		u64 cycles;
+	} contestants[] = {
+		{ .name = "NULL-NOP", .digest = hash_null_nop, .digest_size = 32 },
+		{ .name = "NULL-MEMCPY", .digest = hash_null_memcpy, .digest_size = 32 },
+		{ .name = "CRC32C", .digest = hash_crc32c, .digest_size = 4 },
+		{ .name = "XXHASH", .digest = hash_xxhash, .digest_size = 8 },
+	};
+
+	if (argc > 1) {
+		iterations = atoi(argv[1]);
+		if (iterations < 0)
+			iterations = 1;
+	}
+
+	crc32c_optimization_init();
+	memset(buf, 0, 4096);
+
+	printf("Block size: %d\n", blocksize);
+	printf("Iterations: %d\n", iterations);
+	printf("\n");
+
+	for (idx = 0; idx < ARRAY_SIZE(contestants); idx++) {
+		struct contestant *c = &contestants[idx];
+		u64 start, end;
+
+		printf("% 12s: ", c->name);
+		fflush(stdout);
+
+		start = read_tsc();
+		for (iter = 0; iter < iterations; iter++) {
+			memset(buf, iter & 0xFF, blocksize);
+			memset(hash, 0, 32);
+			c->digest(buf, blocksize, hash);
+		}
+		end = read_tsc();
+		c->cycles = end - start;
+
+		printf("cycles: % 12llu, c/i % 8llu\n",
+				(unsigned long long)c->cycles,
+				(unsigned long long)c->cycles / iterations);
+	}
+
+	return 0;
+}