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To: Julian Elischer <julian@ref.tfs.com>
cc: hackers@FreeBSD.ORG, Jim Lowe <james@miller.cs.uwm.edu>
Subject: Re: Buffer cache , lmbench part 3 
In-reply-to: Your message of "Sun, 29 Oct 1995 20:35:01 PST."
             <199510300435.UAA09703@ref.tfs.com> 
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Date: Sun, 29 Oct 1995 20:59:04 -0800
From: "Amancio Hasty Jr." <hasty@rah.star-gate.com>
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>>> Julian Elischer said:
 > How do you know it's buffer_cache?

Cause that's Jim said ... Not sure if Jim recorded the space launch
on tape. However, I am sure that he can try to record something else
and see if he gets similar results. Currently, I am little handicap because
I can't capture video on FreeBSD , argh... and the video capture at 
least under Windows sucks . Hopefully, in the near future I will
be able to get my Diamond S3 968 + mpeg/video capture daugther card
working on FreeBSD.

Tnks for the tip!!
	Amancio


 > you could put the 'sync' (update) frequency to 1
 > sysctl -w  kern.update=1
 > (I think)
 > and try again..
 > (I presume he has it on tape....)
 > you don't want to go synchronous
 > but you don't want to be so asynchronous that the ram fills up
 > and you end up waiting on disk..
 > 
 > 
 > try this....
 > 
 > 
 > > 
 > > 
 > > Jim Lowe recorded the last space shuttle launch on his FreeBSD box;however
     ,
 > > he ran into a minor gotcha the buffer cache. If you want to see the
 > > buffer cache in action just play the mpeg movie and look for pauses on
 > > on the movie. So the question now is: Is the buffer cache tuneble to
 > > avoid this kind of behavior? 
 > > 
 > > I was thinking that video capture without compression eats up enourmous
 > > amount of disk space so it would not be too unconceivable to bypass the
 > > file system and buffer cache and just do raw I/O to the disk.
 > > 
 > > Here is a pointer to Jim's mpeg version of the space shuttle launch it 
 > > is about 1.7mb and the original was 300MB :
 > > 
 > >  ftp://ftp.cs.uwm.edu/pub/shuttle_gifs/sts73.launch.mpg.
 > > 
 > > 	Enjoy,
 > > 	Amancio
 > > 
 > > 
 > > 
 >