Date: Mon, 19 Apr 2021 23:36:13 -0700 From: Mark Millard <marklmi@yahoo.com> To: Brandon Bergren <bdragon@FreeBSD.org> Cc: FreeBSD PowerPC ML <freebsd-ppc@freebsd.org> Subject: Re: PowerMac G4 booting from memstick image Message-ID: <D7F515C0-9B38-4B73-A966-2D8A16C28E63@yahoo.com> In-Reply-To: <e8df0188-9cde-4c41-964e-af7d1e0fdc39@www.fastmail.com> References: <A0937215-7A85-4250-B387-4175E10591C8@gmail.com> <CAOpTx7Fe%2BYMy=W%2Bs2-qz9V0803xPeqk19qptyG4fwdE5GUY7SQ@mail.gmail.com> <0E36A05F-017F-4B81-80E9-BC27D10E64FD@gmail.com> <800807B2-83C1-40CB-B5D3-67B5A6AED2C7@yahoo.com> <6F45C842-2520-46AF-8818-B1E18107C706@gmail.com> <e8df0188-9cde-4c41-964e-af7d1e0fdc39@www.fastmail.com>
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On 2021-Apr-19, at 18:42, Brandon Bergren <bdragon at FreeBSD.org> wrote: >> . . . >>> On Apr 19, 2021, at 20:46 , Mark Millard <marklmi@yahoo.com> wrote: >>> >>> >>> >>> On 2021-Apr-19, at 16:34, Mehul Sanghvi <mehul.sanghvi at gmail.com> wrote: >>> >>>> . . . >>> >>>> As I understand it 13.0 handles SMP on the G4 better, and since I have a G$ with 2 CPUs, that would be better anyway. >>> >>> . . . >>> >>> Unfortunately, the FreeBSD 32-bit kernel that covers PowerMacs (G3/G4) >>> slowly zeros out pages of user processes that it should not touch. >>> This ends up causing some processes to crash and probably other, less >>> obvious, issues. It is not a reliable environment. To my knowledge, >>> this area is not under active development currently but the basic >>> issue of what type of thing is missing was identified some time back. >>> (The 64-bit kernel that covers G5s does not have this problem.) > > I still haven't been able to reproduce this on G3/G4, but definitely concur that there is a page zeroing issue when attempting to use the 32 bit kernel on a G5 (which has a different MMU -- the kernel interacts with it via bridge mode compatibility. I've tried several times to figure out what the heck is going on but failed every time.) A) Build the system with jemalloc's debugging/internal- valdiation enabled (world). Running the system that results explicitly notices unexpected zeros much earlier than the otherwise indirect consequences of them do. B) Just leaving the system operating with background processes running but basically idle eventually gets process cores from the unexpected zeros. It helps to have a machine that can be left that way instead of needing to be put to other uses. Time to failure varied. I've had the problem shown on both types of G4s and the G3, every non-G5 PowerMac that I currently have access to that has ever managed to boot FreeBSD. (I've access to one that never has, despite MacOSX and various Linux boots.) FYI: My context is still based on: merge-base: 7381bbee29df959e88ec59866cf2878263e7f3b2 merge-base: CommitDate: 2021-03-12 20:29:42 +0000 7381bbee29df (freebsd/main, freebsd/HEAD, pure-src, main) cam: Run all XPT_ASYNC ccbs in a dedicated thread n245444 (--first-parent --count for merge-base) It may be a while before I'd update if such is required for any testing that I might eventually do. As I remember, last I tied I still could not run 32-bit FreeBSD on the G5s that I tried at the time. (Now both basically dead. For the one of the pair that sort of works, if things go very well, I can boot before the G5 overheats. Then it might idle for a while.) Now there is only the 1 core per socket G5 left that can operate for a sustained time with a load --and it seems to be having other problems at times. > By the way, I *FINALLY* figured out what is going on with moused freaking out. It ended up being an oversight in forking that lead to floating point registers getting out of sync. > My current in-testing patch is http://drop.rtk0.net/fork_rework_3.patch -- will be submitting it soon once I finish my local testing. Cool. > This issue actually affects ppc64 as well and has probably been the source of some mystery crashes when forking. Again cool. But my lack of mouse connection/use means I've probably not seen the problem. >>> There is more, but the above two are fairly major items out of the >>> overall list. >>> >>> These issues are not unique to 13.0+ as far as I know. Using 12.x >>> likely would not avoid them. > > IMO 13 is in better shape than 12.x. I am currently dogfooding it on a G4 PowerBook on a daily basis and will be continuing to fix issues here and there that have been cropping up. > === Mark Millard marklmi at yahoo.com ( dsl-only.net went away in early 2018-Mar)home | help
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