From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <38A0BED6.AD2E336C@zeta.org.au> Date: Wed, 09 Feb 2000 12:11:50 +1100 From: Peter Allworth MIME-Version: 1.0 To: Jesper Skov CC: linuxppc-embedded@lists.linuxppc.org, linuxppc-dev@lists.linuxppc.org Subject: more Re: Low memory problems in 8xx Linux References: <20000201235813.4F5611B51A@elph.research.canon.com.au> <38977960.40E014A1@zeta.org.au> Content-Type: text/plain; charset=us-ascii Sender: owner-linuxppc-dev@lists.linuxppc.org List-Id: Jesper Skov wrote: > An alternative and slighly faster implementation might be to skip the > _PAGE_PRESENT check. Any reason something like this wouldn't work? I had another look at the code and I now remember my rationale for the _PAGE_PRESENT test. It wasn't to do with level 1 table entries, Dan's code already takes care of that. It was so that a zeroed pte couldn't get changed to a non-zero value, since that would make the pte_none() function return the wrong result. (Moreover, it just seemed wrong to mess with something that's marked "invalid".) Admittedly I'm being a bit paranoid since the next thing the exception handler is likely to do is set the page table entry to something valid. But, can you be sure? What about a segmentation fault? ;) Cheers, PeterA. "I've always considered a paranoid as a man with all the facts." -- Tales of Ordinary Madness ** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/