hdparm -t yields similiar results on 2.4.18 and 2.5.50. What is a huge
difference is the scattered reads from a disk. At least it is good to
see other people experiencing similiar kernel messages. Would it help to
post the program? Here it is anyway:
Thanks--
Dave
//compile with
//gcc t.c -o t -lpthread
#include <stdio.h>
#include <stdlib.h>
#include <linux/fcntl.h>
#include <unistd.h>
#include <linux/unistd.h>
#include <sys/time.h>
#include <pthread.h>
char DEVNAME[128];
extern long long lseek64(int,long long,int);
unsigned char *tbuff;
long long now(void)
{
struct timeval tv;
gettimeofday(&tv,0);
return tv.tv_sec*1000000ll + tv.tv_usec;
}
int intcomp(const void *v1,const void *v2)
{
return *(unsigned long *)v1 - *(unsigned long *)v2;
}
#define NUM 250
#define BLOCK (188*128*4ll)
int fd;
long long l;
char state[NUM];
void *readfunc(void *a)
{
long long off;
int lfd;
int r;
lfd=open(DEVNAME,O_RDONLY|O_LARGEFILE|O_SYNC);
off=(rand()&0x7fffffff)%l*BLOCK;
lseek64(lfd,off,SEEK_SET);
r=read(lfd,tbuff,BLOCK);
state[(int)a]=1;
close(lfd);
return 0;
}
int main(int argc,char **argv)
{
long long lres;
int res;
int i,j;
long long start,off;
unsigned char *p;
if(argc<2) {printf("specify device to test\n");exit(0);}
strcpy(DEVNAME,argv[1]);
tbuff=malloc(BLOCK+4096);
fd=open(argv[1],O_RDONLY|O_LARGEFILE);
printf("fd=%d\n",fd);
if(fd<0) exit(0);
while((int)tbuff & 4095) ++tbuff; // align to PAGE_SIZE
l=lseek64(fd,0ll,SEEK_END);
printf("Total volume size=%lld megabytes\n",l/0x100000);
l/=BLOCK;
printf("%d blocks\n",l);
start=now();
srand((int)start);
for(i=0;i<NUM;++i)
{
pthread_t tt;
memset(&tt,0,sizeof(tt));
pthread_create(&tt,0,readfunc,(void *)i);
}
for(;;)
{
for(i=0;i<NUM;++i)
if(!state[i]) break;
if(i==NUM) break;
usleep(10000);
}
start=now()-start;
printf("%f seconds\n",start/(float)1000000.0);
printf("%f mbytes/second\n",(float)BLOCK*NUM/start);
return 0;
}
-
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This archive was generated by hypermail 2b29 : Sat Dec 07 2002 - 22:00:29 EST