netdev - Re: [PATCH] CONFIG_PACKET_MMAP should depend on MMU

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Date:	Fri, 20 Apr 2007 09:58:52 +0100
From:	David Howells <dhowells@...hat.com>
To:	"Aubrey Li" <aubreylee@...il.com>
Cc:	"Robin Getz" <rgetz@...ckfin.uclinux.org>, uaca@...mni.uv.es,
	bryan.wu@...log.com, "Alan Cox" <alan@...rguk.ukuu.org.uk>,
	waltje@...lt.nl.mugnet.org, netdev@...r.kernel.org,
	"Andrew Morton" <akpm@...l.org>,
	"Linux Kernel" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] CONFIG_PACKET_MMAP should depend on MMU 

Aubrey Li <aubreylee@...il.com> wrote:

> as checked in packet_set_ring, buffer size must be a multiple of PAGE_SIZE,
> --------------------packet_set_ring------------------------
> if (unlikely(req->tp_block_size & (PAGE_SIZE - 1)))
> 
> So why not use __get_free_pages rather than kmalloc,

Because kmalloc() may be able to get us a smaller chunk of memory.  Actually,
calling __get_free_pages() might be a better, and then release the excess
pages.

> so that we have pagetables to count?

There are no pagetables in NOMMU-mode.

David
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