Ubuntu fread占用过多cache

[john_liqinghan]

最近在ubuntu的平台上碰到这个问题，使用fopen和fread读取文件发现会把ubuntu的cache占用的很大，基本是文件有多大，cache就得有多大？在嵌入式海思的平台上使用，如果使用多个fread读取大文件，就会把cache占用尽了，内存就损耗过度！发生oom killer ， Out of memory这种问题！测试代码如下：

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h>
#include<fcntl.h>

unsigned char *pu8Buf = NULL;
 
void ExitHandleSig(int signo){
	if (SIGINT == signo || SIGTSTP == signo){
		if(pu8Buf != NULL) free(pu8Buf);
		printf("\033[0;31mprogram exit abnormally!\033[0;39m\n");
	}
	exit(0);
}
int main(){

#if 1
	//fread fopen 版本
	FILE *fpStrm=NULL;
   
	int s32UsedBytes = 0, s32ReadLen = 0;
	unsigned int bufSize=1280 * 720  * 3 / 2;
	pu8Buf = (unsigned char*)malloc(bufSize);
	fpStrm = fopen("../videofile/1280_720_H264.h264", "rb");
	if(fpStrm == NULL){
		printf("Can't open file \n");
		exit(0);
	}
	
	signal(SIGINT, ExitHandleSig);
	signal(SIGTERM, ExitHandleSig);
	
	while(1){
		fseek(fpStrm, s32UsedBytes, SEEK_SET);
               s32ReadLen = fread(pu8Buf, 1, bufSize, fpStrm);
		if(s32ReadLen != bufSize){
			printf("end of file \n");
			fseek(fpStrm, 0, SEEK_SET);
			s32UsedBytes = 0;
			s32ReadLen  = 0;
		}
		s32UsedBytes = s32UsedBytes +s32ReadLen ;
		sleep(5);
	}
#else
	//read open 版本

	int fileFd;
	int s32UsedBytes = 0, s32ReadLen = 0;
	unsigned int bufSize=720 * 480  * 3 / 2;
	pu8Buf = (unsigned char*)malloc(bufSize);
	fileFd = open("../videofile/720_480_H264.h264",O_RDONLY,S_IRUSR);
	if(fileFd  == -1)
		printf("Can't open file \n");
	
	signal(SIGINT, ExitHandleSig);
	signal(SIGTERM, ExitHandleSig);
	
	while(1){
		lseek(fileFd, s32UsedBytes, SEEK_SET);
               s32ReadLen = read(fileFd,pu8Buf,bufSize);
		if(s32ReadLen != bufSize){
			printf("end of file \n");
			lseek(fileFd, 0, SEEK_SET);
			s32UsedBytes = 0;
			s32ReadLen  = 0;
		}
		s32UsedBytes = s32UsedBytes +s32ReadLen ;
	        usleep(50000);
	}
#endif
	return 1;
}

无论是fread还是read都会如此！Ubuntu怎么有这个bug？

[C_Rabbit]

关注，现在也在学习这一块

[码农Ben]

Linux系统在进行文件读写时都会用到缓存。这些缓存的释放不是立刻执行的。计时用了fclose还不会立刻释放。 考虑用posix_fadvise函数加上POSIX_FADV_DONTNEED来释放。 我在连续多次读写文件时都会这么做。 参考下一下两篇博文： http://leoncom.org/?p=650719 http://blog.yufeng.info/archives/1917

[john_liqinghan]

实在无法找到很满意的答案，好内存确实是存在！只能手动清除cache！