Ubuntu fread占用过多cache

2016-03-03 11:42:19 300 阅读 AI 写同款 · GEO 优化AI 选题数据监测一键分发 ›

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MySQL BLOB存图片的实战决策指南：Ubuntu 20.04 + PHP深度避坑 BLOB（Binary Large Object）是关系型数据库中存储二进制大对象的基础机制，其核心原理在于将文件数据作为字段值嵌入事务引擎（如InnoDB），从而保障ACID一致性与备份原子性。相比文件路径引用，BLOB的技术价值体现在强事务绑定、权限统一管控、分布式路径解耦及运维收敛性，但代价是显著增加磁盘IO、内存压力与网络传输开销。典型应用场景包括金融开户凭证、医疗影像元数据、政务审批附件等对数据不可分割性有硬性合规要求的系统。本文聚焦Ubuntu 20.04环境下PHP与MySQL协同操作BLOB 阅读详情

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;

}