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Date:      Tue, 08 Aug 2000 18:03:08 CEST
From:      Mitja Horvat <mitja.horvat@hermes.si>
To:        freebsd-hackers@freebsd.org
Subject:   4.1-RELEASE problem writing to async mounted filesystem
Message-ID:  <200008081606.SAA11004@akira.hermes.si>

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Hi,

I recently upgraded to FreeBSD 4.1-RELEASE(CD image). I noticed that while
writing
to an asynchronously mounted filesystem(mount -o async / ...) all other IO
operations to the FS are almost blocked. I have only one asynchronously
mounted 
partition(/) and the following shell script makes the machine unresponsive
so I cannot
even telnet to it:

while true; do rm -f foo; dd if=/dev/zero of=foo bs=1024k count=256; done

4.0-RELEASE does a much better job at handling similar situations... 

I'm using softupdates, but even without them the problem persists. 

This does not happen if the fs is mounted synchronously, but I also get
MUCH slower IO
throughput(800kb/s compared to 12MB/s with async). 

I know that mounting filesystems asynchronously is dangerous, but this is
my workstation
and is being backed up on a daily basis, so a filesystem crash is not
something I'm 
worried about... 

I suspect this is something related to the buffer code and currently have
no much time to 
inspect that. 

Can somebody give me a hint how to solve the problem?

Thank you,
Mitja



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