From: Dan Malek <dan@mvista•com>
To: Ralph Blach <rcblach@raleigh•ibm.com>
Cc: frowand@mvista•com, linuxppc-dev <linuxppc-dev@lists•linuxppc.org>
Subject: Re: kernel mapping
Date: Tue, 16 Jan 2001 11:50:15 -0500 [thread overview]
Message-ID: <3A647BC7.15F669F3@mvista.com> (raw)
In-Reply-To: 3A643283.A20200E8@raleigh.ibm.com
Ralph Blach wrote:
>
> Why do we need simulated bat registers.
To improve performance. Right now, on the 4xx there is the
concept of "pinned" TLB entries to reduce/eliminate TLB misses
on large mapped areas (like kernel text/data or I/O). The 8xx
does this in some custom applications as well. These are just
hacks that are headed down a disastrous maintenance path that
need to be stopped now for a more generic solution.
I have been experimenting with many different methods of using
the "large" page table sizes through the generic memory management
methods that already exist in the kernel. I believe I can wrap
the concept of the pinned TLB entries into the same logic as BAT
register management on the bigger processors. Hence, I call them
simulated BAT registers....the semantics aren't quite the same.
The BAT registers are a really good thing, and although the large
page size TLB entries are more flexible, they require more software
overhead. I would like to make some generic Linux MM modifications
to help us support variable page sizes, but I suspect that will
never happen.
-- Dan
** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/
next prev parent reply other threads:[~2001-01-16 16:50 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-01-15 23:13 kernel mapping Dan Malek
2001-01-16 3:07 ` Frank Rowand
2001-01-16 3:55 ` Dan Malek
2001-01-16 11:37 ` Ralph Blach
2001-01-16 16:50 ` Dan Malek [this message]
2001-01-16 17:10 ` Ralph Blach
2001-01-16 17:47 ` David Edelsohn
2001-01-16 21:57 ` Dan Malek
2001-01-17 10:51 ` Gabriel Paubert
2001-01-17 17:45 ` David Edelsohn
2001-01-16 19:56 ` Frank Rowand
2001-01-16 22:13 ` Dan Malek
2001-01-17 0:04 ` Frank Rowand
2001-01-17 7:02 ` Dan Malek
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