From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <3A648075.5093ADAD@raleigh.ibm.com> Date: Tue, 16 Jan 2001 12:10:13 -0500 From: Ralph Blach MIME-Version: 1.0 To: Dan Malek CC: frowand@mvista.com, linuxppc-dev Subject: Re: kernel mapping References: <3A63840E.4C724E03@mvista.com> <3A63BAFB.80E3980C@mvista.com> <3A643283.A20200E8@raleigh.ibm.com> <3A647BC7.15F669F3@mvista.com> Content-Type: multipart/mixed; boundary="------------554DCBF0614BA50A52687995" Sender: owner-linuxppc-dev@lists.linuxppc.org List-Id: This is a multi-part message in MIME format. --------------554DCBF0614BA50A52687995 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Dan, Thanks for the info. I agree that Pinned tlbs could be maintence headache with each 4xx/8xx chip requiring a different set of pinned tlbs. Chip Dan Malek wrote: > > 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 > --------------554DCBF0614BA50A52687995 Content-Type: text/x-vcard; charset=us-ascii; name="rcblach.vcf" Content-Description: Card for Ralph Blach Content-Disposition: attachment; filename="rcblach.vcf" Content-Transfer-Encoding: 7bit begin:vcard n:Blach;Ralph tel;work:919-543-1207 x-mozilla-html:TRUE url:www.ibm.com org:IBM MicroElectronics adr:;;3039 Cornwallis ;RTP;NC;27709;USA version:2.1 email;internet:rcblach@raleigh.ibm.com x-mozilla-cpt:;15936 fn:Ralph Blach end:vcard --------------554DCBF0614BA50A52687995-- ** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/