From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paul Mackerras MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Message-ID: <14784.22458.21233.588776@argo.linuxcare.com.au> Date: Thu, 14 Sep 2000 15:44:42 +1100 (EST) To: mlan@cpu.lu Cc: linuxppc-dev@lists.linuxppc.org Subject: Re: zeroing pages in the idle task? In-Reply-To: <200009131951.VAA00816@piglet.grunz.lu> References: <200009122018.WAA00786@piglet.grunz.lu> <200009131951.VAA00816@piglet.grunz.lu> Reply-To: paulus@linuxcare.com.au Sender: owner-linuxppc-dev@lists.linuxppc.org List-Id: Michel Lanners writes: > > - if not, would it be a good idea to enable it by default? > > What do you think, Paul, Cort? As I recall, it was necessary to disable the cache in the idle task so that the idle task's clearing of pages didn't trash the cache for other tasks. This introduces its own set of complexities, for example you have to make sure the cache is reenabled on all exception entries and also before you call schedule in the idle task. You also have to make sure that you don't get any inconsistencies in the cache, which means you would have to flush the cache for the page before starting to clear it with the cache disabled. It would be cleaner to have the page mapped with a non-cacheable mapping while the idle task is clearing it but you still have to be careful about cache inconsistencies, particularly if the page is mapped twice and one mapping is cacheable and the other isn't. I'm not sure that the current code still addresses all those issues correctly and completely. Unused things tend to be subject to bitrot. :-) Paul. -- Paul Mackerras, Senior Open Source Researcher, Linuxcare, Inc. +61 2 6262 8990 tel, +61 2 6262 8991 fax paulus@linuxcare.com.au, http://www.linuxcare.com.au/ Linuxcare. Support for the revolution. ** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/