question about memcpy in libc

Hi,

I’m confused when I use memcpy() in pandaboard android. The test code is very simple, as below:

#define PER_COPY_SIZE (1024*1024*4)

int main(int argc, char *argv[ ]){

char *src;

char *dst;

char *p;

src=(char *)malloc(PER_COPY_SIZE);

dst=(char*)malloc(PER_COPY_SIZE);

p=src;

#if 1

for(int i=0; i<PER_COPY_SIZE; i++){

*p++=i%255;

}

#endif

for(int j=0; j<1000; j++){

memcpy(dst, src, PER_COPY_SIZE);

}

free(src);

free(dst);

return 0;

}

It copies 4M byte data from source to dest repeatedly and takes 12 seconds. But when I get rid of the part of code in red color, it takes only 4 seconds. Why does the writing to source firstly has influence the memcpy( ) time so greatly?

Thanks & Best Regards! 牟刚 Actions Semiconductor Co.,Ltd Tel: +86-756-3392353 ext.3103 Fax: +86-756-3392251 Email: mugang@actions-semi.com HTTP://www.actions-semi.com

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发件人: 牟刚 发送时间: 2012年10月30日 16:04 收件人: 'linaro-android@lists.linaro.org' 主题: pandaboard GPU driver

Hi，

I want compile pandaboard GPU driver myself and get the library, such as “libEGL_POWERVR_SGX540_120.so”, “libIMGegl.so” and so on. How can I get the GPU driver source code and compile environment?

Thanks & Best Regards! 牟刚 Actions Semiconductor Co.,Ltd Tel: +86-756-3392353 ext.3103 Fax: +86-756-3392251 Email: mugang@actions-semi.com HTTP://www.actions-semi.com