Simple kernel module to test speed of fp and int operation

README.md

執行 make，會編譯並紀錄測試結果，輸出檔案名稱為 compare.png

** 注意！！ dmesg 中的紀錄會被刪除，若有需要請事先備份 **

floating.c

#include <linux/init.h>
#include <linux/module.h>
#include <linux/random.h>
#pragma GCC optimize ("O0")
#define MAX_ITER 1000000
#define ADD_ONCE 1000

MODULE_DESCRIPTION("Kernel module with floating point operation");
MODULE_LICENSE("Dual MIT/GPL");

static int __init float_init(void) {
    long long int start, end;
    for (int j=0; j<MAX_ITER; j+=ADD_ONCE) {
#ifdef INTEGER_OP
        int a, b, c;
        get_random_bytes(&a, sizeof(a));
        get_random_bytes(&b, sizeof(b));
#else
        int x, y;
        float a, b, c;
        get_random_bytes(&x, sizeof(x));
        get_random_bytes(&y, sizeof(y));
        a = (float)x + (float)1.0/b;

        get_random_bytes(&x, sizeof(x));
        get_random_bytes(&y, sizeof(y));
        b = (float)x + (float)1.0/b;
#endif

        start = ktime_get_ns();
#ifdef INTEGER_OP
        for (int i=0; i < j; ++i) {
            c = a*b;
        }
#else
        for (int i=0; i < j; ++i) {
            c = a*b;
        }
#endif
        end = ktime_get_ns();

        printk(KERN_DEBUG "%d %lld", j, end-start);
    }

    return 0;
}

static void __exit float_exit(void) {
}

module_init(float_init);
module_exit(float_exit);

Makefile

PWD := $(shell pwd)
KDIR = /usr/src/linux-headers-$(shell uname -r)/

MODULE_NAME = floating
obj-m := $(MODULE_NAME).o
ccflags-y := -std=gnu99 -Wno-declaration-after-statement -mhard-float

all: clean integer_ver float_ver
	gnuplot plot.gp

integer_ver:
	$(MAKE) -C $(KDIR) M=$(PWD) modules EXTRA_CFLAGS='-DINTEGER_OP -DOPERATION=\"INTEGER\"'
	$(MAKE) run
	dmesg -f kern | cut -d ' ' -f 2- >> integer.out
float_ver:
	$(MAKE) -C $(KDIR) M=$(PWD) modules EXTRA_CFLAGS='-DFLOAT_OP -DOPERATION=\"FLOAT\"'
	$(MAKE) run
	dmesg -f kern | cut -d ' ' -f 2- >> float.out

run:
	-$(MAKE) unload
	sudo dmesg -C
	$(MAKE) load
	$(MAKE) unload

load:
	sudo insmod floating.ko
unload:
	sudo rmmod floating.ko
clean:
	sudo dmesg -C
	$(MAKE) -C $(KDIR) M=$(PWD) clean
	$(RM) *.out compare.png

plot.gp

set terminal png
set output 'compare.png'

set xlabel 'number of iterations'
set ylabel 'times (ns)'

plot 'integer.out' using 1:2 title "Integer", \
     'float.out'  using 1:2 title "Floating point"