From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from digitaldans.com (digitaldans.com [69.36.177.99]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id A21B4B71AB for ; Tue, 11 Oct 2011 05:04:27 +1100 (EST) Message-Id: <9CE82FAD-2451-4253-B304-CF8BE5AC8CAC@digitaldans.com> From: Dan Malek To: Joakim Tjernlund In-Reply-To: Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes Mime-Version: 1.0 (Apple Message framework v936) Subject: Re: [PATCH 0/3] 8xx: Large page(8MB) support for 2.4 Date: Mon, 10 Oct 2011 11:03:53 -0700 References: <1318246714-5015-1-git-send-email-Joakim.Tjernlund@transmode.se> <39B024CE-70A2-4D32-A29C-5702C7D2D6CF@digitaldans.com> Cc: Scott Wood , linuxppc-dev , Willy Tarreau List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Oct 10, 2011, at 9:45 AM, Joakim Tjernlund wrote: > That is an easy port but I will have to do that blind. Would you > mind take this for a spin on 2.4 first? My current system is running 2.6, so I don't have much interested in testing 2.4 > The more interesting part is if one should use other sized(16K or > 512K) large pages too? My thought long ago was most of the 8xx systems have rather small real memories, so the larger pages, especially 512K may be too wasteful. I've always been a fan of keeping the TLB handlers tiny and simple, rather then spending the instructions doing complex replacements. Remember, this also affects the I- and D-cache, so a more frequent and trivial PTE update could very well gain larger system performance than the management of larger pages with more complex code. With all of the bug fix code in the handlers, maybe a larger page would be better. > Those should be useful for user space but it is a lot of work. I > haven't checked > what large page support for user space is in 2.6 for ppc though. The 2.6/3.0 kernel supports different, but fixed, page sizes. IIRC, anything over 64K may require distribution rebuilding to realign code/data sections to more restrictive boundaries. Maybe a 16K page would show some benefit. I'll try to make some time to play with it. Thanks. -- Dan