Subject: Re: Patch for two mbuf dma optimizations
To: None <>
From: Jason R Thorpe <>
List: tech-kern
Date: 03/29/2003 13:32:28
On Sun, Mar 30, 2003 at 06:12:36AM +0900, wrote:

 > >  /* description of external storage mapped into mbuf, valid if M_EXT set */
 > >  struct m_ext {
 > >  	caddr_t	ext_buf;		/* start of buffer */
 > 	is it a correct assumption that a page is 4K or smaller?  4096 should
 > 	be some constant from other headers (sys/ARCH/include/BLAH), i guess?

Problem is that PAGE_SIZE and/or NBPG isn't a constant on some platforms,
and this value needs to be a constant.

I'm pretty sure we don't have any platforms where the page size presented
to the OS is < 4K.  The worst that can happen on platforms where the page
size is > 4K is that we burn a few extra bytes for unused pointers.

        -- Jason R. Thorpe <>