From owner-freebsd-hackers  Fri Dec  4 13:05:01 1998
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Date: Fri, 4 Dec 1998 13:03:29 -0800 (PST)
From: Julian Elischer <julian@whistle.com>
To: Archie Cobbs <archie@whistle.com>
cc: freebsd-hackers@FreeBSD.ORG
Subject: Re: Help with clist_alloc_cblocks()
In-Reply-To: <199812042028.MAA06497@bubba.whistle.com>
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check kern/tty_subr.c around line 150 on.

values of 0 for the last 2 args will allocate exactly 1 cblock
(the way I read it)

that is 128 - 16 - 4 == 108 bytes of storage.
the arguments are ccmax (above which the list will not be grown)
and ccreserve, ( below which the allocated cblocks will not be freed)
a value of 0 sets each to 1 cblock.

you probably want to use values of 1000, 300 or something.


On Fri, 4 Dec 1998, Archie Cobbs wrote:

> Hello,
> I'm trying to write a line discipline, roughly similar to the PPP
> line discipline. My question is, what are the correct parameters to
> give to clist_alloc_cblocks()?
> 
>   /*
>    * Pre-allocate cblocks to the an appropriate amount.
>    */
> 
>     ttyflush(tp, FREAD | FWRITE);
>     clist_alloc_cblocks(&tp->t_canq, 0, 0);
>     clist_alloc_cblocks(&tp->t_rawq, 0, 0); 	/* XXX probably wrong! */
>     clist_alloc_cblocks(&tp->t_outq, MLEN + NGT_HIWATER, MLEN + NGT_HIWATER);
> 
> I'm not sure how to determine what the correct values to call
> clist_alloc_cblocks() should be. The values I'm using now cause a
> bunch of "interrupt-level buffer overflows" reported from the sio
> driver. It looks like I can simply increase the values for tp->t_rawq
> but I'd like to understand exactly what they mean first.
> 
> Thanks,
> -Archie
> 
> ___________________________________________________________________________
> Archie Cobbs   *   Whistle Communications, Inc.  *   http://www.whistle.com
> 
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