From 3bb12208fb873ad02e28802c6b4f8dcc9d2311b9 Mon Sep 17 00:00:00 2001
From: Florian Fischer <florian.fischer@muhq.space>
Date: Mon, 2 Aug 2021 11:37:02 +0200
Subject: [PATCH] use uint64_t for cycles and average calculation
---
Makefile | 4 +++-
bench.c | 10 +++++++---
stopwatch.c | 4 ++--
stopwatch.h | 8 ++++----
4 files changed, 16 insertions(+), 10 deletions(-)
diff --git a/Makefile b/Makefile
index bbc1e08..a9ced29 100644
--- a/Makefile
+++ b/Makefile
@@ -8,7 +8,7 @@ LDFLAGS := -luring -pthread -lrt
CFLAGS := -Werror -Wall -g -O3
# CFLAGS := -Werror -Wall -g -O0
-.PHONY: all clean eval docker-eval
+.PHONY: all clean eval docker-eval check
eval: all
@for syscall in $(SYSCALLS); do echo -n "$$syscall " ; ./bench-$$syscall; done
@@ -28,6 +28,8 @@ $(foreach syscall,$(SYSCALLS),$(eval $(call generateTargets,$(syscall))))
clean:
rm -f $(OBJ)
+check: tidy check-format
+
tidy:
clang-tidy *.c
diff --git a/bench.c b/bench.c
index 7a3c941..b7439a6 100644
--- a/bench.c
+++ b/bench.c
@@ -42,8 +42,12 @@ int main() {
errx(EXIT_FAILURE, "cycles overflowed at %ld", i);
}
- double avg_nanos = nanos_sum / (double)iterations;
- double avg_cycles = cycles_sum / (double)iterations;
- printf("%lf ns, %lf cycles\n", avg_nanos, avg_cycles);
+ // Since uint64_t <-> double conversion are not well defined
+ // and we use really small units (cycles and nanoseconds) I am willing
+ // to accept that we throw away anything after the decimal point.
+ uint64_t avg_nanos = nanos_sum / iterations;
+ uint64_t avg_cycles = cycles_sum / iterations;
+
+ printf("%lu ns, %lu cycles\n", avg_nanos, avg_cycles);
return 0;
}
diff --git a/stopwatch.c b/stopwatch.c
index aaf5028..472baf5 100644
--- a/stopwatch.c
+++ b/stopwatch.c
@@ -1,6 +1,6 @@
#include "stopwatch.h"
-int64_t cycles_start, cycles_stop;
+uint64_t cycles_start, cycles_stop;
struct timespec start, stop;
int64_t sec_to_nanos(int64_t sec) { return sec * 1000 * 1000 * 1000; }
@@ -13,4 +13,4 @@ int64_t clock_diff_nanos() {
return nanos;
}
-int64_t clock_diff_cycles() { return cycles_stop - cycles_start; }
+uint64_t clock_diff_cycles() { return cycles_stop - cycles_start; }
diff --git a/stopwatch.h b/stopwatch.h
index 6830f97..7b670d1 100644
--- a/stopwatch.h
+++ b/stopwatch.h
@@ -3,17 +3,17 @@
#include <stdint.h>
#include <time.h>
-extern int64_t cycles_start, cycles_stop;
+extern uint64_t cycles_start, cycles_stop;
extern struct timespec start, stop;
-static __inline__ int64_t rdtsc_s(void) {
+static __inline__ uint64_t rdtsc_s(void) {
unsigned a, d;
asm volatile("cpuid" ::: "%rax", "%rbx", "%rcx", "%rdx");
asm volatile("rdtsc" : "=a"(a), "=d"(d));
return ((unsigned long)a) | (((unsigned long)d) << 32);
}
-static __inline__ int64_t rdtsc_e(void) {
+static __inline__ uint64_t rdtsc_e(void) {
unsigned a, d;
asm volatile("rdtscp" : "=a"(a), "=d"(d));
asm volatile("cpuid" ::: "%rax", "%rbx", "%rcx", "%rdx");
@@ -30,7 +30,7 @@ static inline void stop_watch() {
clock_gettime(CLOCK_MONOTONIC, &stop);
}
-int64_t clock_diff_cycles();
+uint64_t clock_diff_cycles();
int64_t clock_diff_nanos();
double nanos_to_millis(int64_t nanos);
int64_t sec_to_nanos(int64_t sec);
--
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