From owner-freebsd-hackers  Mon Mar 10 23:27:51 1997
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Date: Tue, 11 Mar 1997 16:27:30 +0900 (JST)
From: Michael Hancock <michaelh@cet.co.jp>
To: Tom Samplonius <tom@sdf.com>
cc: Brian Tao <taob@vex.net>, "matthew c. mead" <mmead@goof.com>,
        isp@freebsd.org, hackers@freebsd.org
Subject: Maxcontig for news server (was Re: freebsd as a news server?)
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On Mon, 10 Mar 1997, Tom Samplonius wrote:

> > > On Tue, 11 Mar 1997, Michael Hancock wrote:
> > > 
> > > ...
> > > > I've been using -i 3072 -b 4096 -f 1024 -a 8 for non-binary newsgroups and
> > > > the default for binary newsgroups.
> > > > 
> > > > This way news articles on average will fit in a block.
> > > 
> > >   You always want maxcontig to beigger than 8.  It has nothing to do with
> > > file allocation, only have many sectors are transfered at once to the
> > > driver.
> > 
> > And the magic number is ____.
> 
>   As big as possible.  All the disk drivers should be able to handle at
> least 128.  I don't really know how big it can be.  256?  1024?
 
>   A too small maxcontig will hamper scatter/gather.  I noticed that by
> looking at the sps and tps values from iostat that it was never
> transfering more than 16 sectors per transfer.  I bumped up maxcontig, and
> noticed a nice performance increase (at least for my application).

Was your application INND?

>   The default maxcontig setting for 2.1.x is just way too small.

The default is 8 assuming a bsize of 8K, the man pages say it's 1.

        if (maxcontig == 0)
                maxcontig = MAX(1, MAXPHYS / bsize - 1);

MAXPHYS is 64K.

Regards,


Mike