我的简单程序:
//usage:
//indent ./a.c;gcc -O0 ./a.c
//./a.out max r/w repeat timeout
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
int
main (int argc, char **argv)
{
time_t const start_time = time (NULL);
time_t timeout;
int max;
int repeat;
if (argc == 5)
{
max = atoi (argv[1]);
repeat = atoi (argv[3]);
timeout = ((time_t) (atoi (argv[4])));
}
else
return 1;
unsigned char **block_array =
calloc (sizeof (unsigned char *), (size_t) (max));
size_t block_length = (size_t) (1024u * 1024u);
unsigned char data[3];
data[0] = 'a';
data[1] = 'b';
data[2] = 'c';
unsigned i = 0u;
//initialize block_array
for (i = 0u; i < max; i++)
{
do
{
if ((timeout > ((time_t) (0)))
&& ((time (NULL) - start_time) > timeout))
{
puts ("timeouted!");
return 0;
}
block_array[i] = malloc (block_length);
if (block_array[i] != NULL)
{
unsigned bi = 0u;
for (bi = 0u; bi < block_length; bi++)
block_array[i][bi] = data[bi % ((unsigned) (sizeof (data)))];
}
else
{
printf ("%u error\n", i);
}
}
while (NULL == block_array[i]);
}
puts ("init ok");
unsigned score = 0u;
//do page read test
if ('r' == argv[2][0])
for (;;)
{
for (i = 0u; i < max; i++)
{
if ((timeout > ((time_t) (0)))
&& ((time (NULL) - start_time) > timeout))
{
puts ("timeouted!");
goto show_score;
}
unsigned bi = 0u;
for (bi = 0u; bi < block_length; bi++)
{
data[bi % ((unsigned) (sizeof (data)))] = block_array[i][bi];
}
score++;
}
if (repeat >= 0)
{
repeat--;
if (0 == repeat)
goto show_score;
}
}
//do page write test
else if ('w' == argv[2][0])
for (;;)
{
for (i = 0u; i < max; i++)
{
if ((timeout > ((time_t) (0)))
&& ((time (NULL) - start_time) > timeout))
{
puts ("timeouted!");
goto show_score;
}
unsigned bi = 0u;
for (bi = 0u; bi < block_length; bi++)
{
block_array[i][bi] = data[bi % ((unsigned) (sizeof (data)))];
}
score++;
}
if (repeat >= 0)
{
repeat--;
if (0 == repeat)
goto show_score;
}
}
show_score:
printf ("score:%u\n", score);
return 0;
}
我同样测试了 Debian Jessie(Linux 3.16)(较少测试)和 Debian Stretch(Linux 4.9)(更多测试肯定)
我已经重复多次相同的测试来确定这一点,所以我只发布一个简短的结果。
测试结果:
$ cat /proc/meminfo |grep SwapTotal
SwapTotal: 0 kB
$ time ./a.out 100 r 5 -1
init ok
score:500
real 0m2.689s
user 0m2.604s
sys 0m0.080s
$ time ./a.out 100 w 5 -1
init ok
score:500
real 0m2.567s
user 0m2.496s
sys 0m0.060s
$
最佳答案
在“r”和“w”两种情况下,循环内的主要赋值都是从内存中读取并写回内存,即它们本质上是相同的——您并不是在真正测试内存读取与内存写入。事实证明,每种情况下的时间都非常接近。
'w' 的情况可能会稍微快一些,因为缓存可能包含您想要从内存中读取的值,因为在这种情况下您没有更改源地址。
关于linux - 为什么我的程序存储器写入速度比读取速度快?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/45344563/