From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Tue, 30 Oct 2001 13:05:46 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Tue, 30 Oct 2001 13:05:36 -0500 Received: from hq.fsmlabs.com ([209.155.42.197]:7428 "EHLO hq.fsmlabs.com") by vger.kernel.org with ESMTP id ; Tue, 30 Oct 2001 13:05:26 -0500 Date: Tue, 30 Oct 2001 11:01:31 -0700 From: Cort Dougan To: Linus Torvalds Cc: Victor Yodaiken , Rik van Riel , Andrea Arcangeli , Benjamin LaHaise , "David S. Miller" , linux-kernel@vger.kernel.org Subject: Re: please revert bogus patch to vmscan.c Message-ID: <20011030110131.A11419@ftsoj.fsmlabs.com> In-Reply-To: <20011030095757.A9956@hq2> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5i In-Reply-To: ; from torvalds@transmeta.com on Tue, Oct 30, 2001 at 09:17:31AM -0800 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Actually, they swung the pendelum the other way for the 64-bit chips. The VSID's (MM contexts) are indirectly accessed via a hash-table (with an on chip TLB-style cache called a SLB). The speedup from using the software table-walk actually came from emulating x86 instead of using the native hash tables. Pretty slick that emulating a 30-year old MMU and improves performance on the PowerPC, eh? There was an April Fools Microprocessor reports describing a processor that had gone 64-bit and had a "twisted gothic nightmare of twisted logic" based MMU that involved XOR-ing addresses with random numbers. They were unwittingly predicting the future of the PPC MMU. The nightmares and shakes have never ended for me, either. Sorry about that, man. } Gods, I hope they have reconsidered that in their 64-bit chips. The 32-bit } hash chains may be ugly, but the architected 32/64-bit MMU stuff is just } so incredibly baroque that it makes any other MMU look positively } beautiful ("Segments? Segments shmegments. Big deal"). } } I still have the occasional nightmares about the IBM block diagrams } "explaining" the PowerPC MMU in their technical documentation. } } There's probably a perfectly valid explanation for them, though (*). } } Linus } } (*) Probably along the lines of the designers being so high on LSD that } they thought it was a really cool idea. That would certainly explain it in } a very logical fashion. } } - } To unsubscribe from this list: send the line "unsubscribe linux-kernel" in } the body of a message to majordomo@vger.kernel.org } More majordomo info at http://vger.kernel.org/majordomo-info.html } Please read the FAQ at http://www.tux.org/lkml/