From nobody@FreeBSD.ORG Thu Jun 24 12:29:32 1999
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Date: Thu, 24 Jun 1999 12:29:32 -0700 (PDT)
From: schuerge@cs.uni-sb.de
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Subject: Serious performance with CPU-intensive processes in the background
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>Number:         12379
>Category:       kern
>Synopsis:       Serious performance with CPU-intensive processes in the background
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          closed
>Quarter:        
>Keywords:       
>Date-Required:  
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Thu Jun 24 12:30:01 PDT 1999
>Closed-Date:    Thu Jun 24 12:45:24 PDT 1999
>Last-Modified:  Thu Jun 24 12:46:20 PDT 1999
>Originator:     Thomas Schrger
>Release:        FreeBSD 4.0-CURRENT
>Organization:
University of Saarbrcken, Germany
>Environment:
FreeBSD starfire.heim-d.uni-sb.de 4.0-CURRENT FreeBSD 4.0-CURRENT #0: Tue Jun 15 13:36:03 CEST 1999     schuerge@starfire.heim-d.uni-sb.de:/usr/src/sys/compile/STARFIRE  i386
Running on dual PII/400 with 256 MB RAM, UW-SCSI and UDMA drive.
>Description:
FreeBSD's system performance is greatly affected when running a very
CPU-intensive (not I/O-intensive) process in the background. I have
tested it with RC5DES (misc/rc5des) and seti@home (astro/setiathome),
but it seems to be a general problem. Note that these two programs
nearly don't do any I/O at all (just receiving/sending blocks after
some hours or days).

When such a process is running in the background (niced to +20), other
I/O-intensive processes in the foreground suffer a lot from it. Transfers
over the LAN become a lot slower, hardisk accesses are slower and also
floppy disk transfers become slower.

I have a directory on my machine that is exported via NFS. When nothing's
in the background, an "ls" in the directory(containing hundreds of files)
on the remote machine takes about 0.5 seconds. With a CPU-intensive process
in the background on my machine, it takes 3 to 4 seconds. Network transfers
drop from e.g 500 KB/sec to 250-300 KB/sec and updating the ports takes
about twice as long when such process is present.

I haven't done more tests, but it seems to me that FreeBSD's performance
noticably drops down to a level that is not really acceptable.
I haven't heard of such problems on other Unix variants.

>How-To-Repeat:
Start some long-runner in the background and compare network I/O speeds
to the system not running the process.

>Fix:


>Release-Note:
>Audit-Trail:
State-Changed-From-To: open->closed 
State-Changed-By: mpp 
State-Changed-When: Thu Jun 24 12:45:24 PDT 1999 
State-Changed-Why:  
Duplicate of kern/12380 (I kept that one open because it had a better 
synopsis). 
>Unformatted:
