>Number:         9212
>Category:       kern
>Synopsis:       File system access slows down after weeks of uptime
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    kern-bug-people (Kernel Bug People)
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Jan 16 18:42:00 2000
>Last-Modified:
>Originator:     Andreas Gustafsson
>Organization:
Nominum, Inc.
>Release:        19991223
>Environment:

System: NetBSD trebuchet.rc.vix.com 1.4P NetBSD 1.4P (TREBUCHET) #0: Thu Dec 23 22:42:19 PST 1999 gson@trebuchet.rc.vix.com:/usr/src/sys/arch/i386/compile/TREBUCHET i386

>Description:

My machine works flawlessly for a week or two after being rebooted.
Then compilations and other disk intensive activities suddenly start
taking many times longer than usual, and are accompanied by the rattle
of constant disk accesses.  I'm sure the machine is not swapping:
pstat -s says it is using only 8 out of 3336480 swap blocks.  Rather,
it seems as if the buffer cache somehow loses its effectiveness.

On the machine in case (550 MHz AMD Athlon, 256 MB RAM, IDE disk),
executing the command

  find /usr/share/man -print >/dev/null

for the first time after a reboot takes 2.2 seconds of real time.
Subsequent invocations usually take only 0.04 seconds (!), no doubt
thanks to the buffer cache.  However, when the machine is experiencing
the slowdown, each invocation takes 1.2 seconds, or 30 times the
usual.

Rebooting the machine fixes the problem, but it returns after 1-3
weeks of uptime.  It has now happened three times.

I have not enabled SOFTDEP, in case that makes a difference. 

>How-To-Repeat:

See above.

>Fix:

Unknown.
>Audit-Trail:
>Unformatted: