Subject: Re: buffer cache tuning - running out of kernel virtual space
To: None <>
From: YAMAMOTO Takashi <>
List: tech-kern
Date: 12/11/2005 11:49:21
> I see that a mechanism already exists to limit virtual space usage by
> the buffer cache, buf_setvalimit(), which is used by alpha, mips, sparc
> and vax.  however, it seems to me that the usage for all but sparc is wrong
> since it sets the limit to whatever the limit would have been anyway:
> 	bufsz = buf_memcalc();
> 	buf_setvalimit(bufsz);
> or maybe this is just supposed to keep people from tuning the limit higher
> than its original value.  I'm not sure why that would be desirable though.
> does anyone know why these are here?  if not, I'll remove them.  (the sparc
> instance actually imposes a smaller limit, so I'll leave that one.)

i guess these are here in order to fix and calculate the necessary amount
of kernel PTEs, esp. for ports without pmap_growkernel.