>Number:         17241
>Category:       kern
>Synopsis:       system chokes when heavy writing/copying to disk huge files
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Jun 12 13:55:01 PDT 2002
>Closed-Date:
>Last-Modified:
>Originator:     Wojciech Puchar
>Release:        1.6B1
>Organization:
TENSOR ap
>Environment:
NetBSD chylonia.3miasto.net 1.6_BETA2 NetBSD 1.6_BETA2 (local) #0: Tue Jun 11 19:45:15 UTC 2002     wojtek@chylonia.3miasto.net:/home/wojtek/kernel/local i386

>Description:
when large I/O with writes are made to disk system chokes generating huge delays
when using programs. it's even with programs that does NO disk I/O and even no memory op

>How-To-Repeat:
compile and run that program on one terminal

> #include <stdio.h>
> const char wind[4]={'|','/','-','\\'};
> main() {
>  int count=0;
>  while(1) {
>   printf("%c\r",wind[(count++)&3]);
>   fflush(stdout);
>   sleep(1);}}

and then start copying huge (>>100MB) file from one disk to another and observe
rotation displayed from this program.

delays even more than 1s can be observer every 5-10 seconds.

same program works perfect without delays on CPU-bound system loads >10 

cp process takes <15% CPU on my system.

>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted: