On 2023-03-07 18:52, Anders Magnusson wrote:
Den 2023-03-07 kl. 18:23, skrev Johnny Billquist:With NetBSD I have had problems even with less than 512M, but the exact mode of failure might vary. But something goes wrong when there is too much memory. 128M works fine. I seem to remember that I've never even got 256M to boot with any version.I doubt it's anything recent. I think the problem have been there since before the dawn of time with NetBSD/vax.When I have some time, I'd be happy to help out a bit more, and try to dig through my memory of things around this that I've done in the past, but a little short on time right now.I think I might have talked with Ragge about it in the past as well, and it might be that he have some more ideas...Maybe.It just sounds odd to me as well, but there is one thing that should not affect the kernel, but maybe - the kernel maps all of physical memory onto S0 space. I don't know how that would affect the CAS code.You were involved in writing the CAS code Johnny, weren't you?
A bit indirectly. I did go over it a bunch many years ago because I wanted to try and get NetBSD to use the native VAX instructions for locks in the kernel. I more or less got it all working, but some parts of the kernel are really depending on very CAS specific semantics, which made it almost impossible to get native locking instructions to work properly in NetBSD. Sadly.
Seems silly to jump through all the hoops of emulating CAS on the VAX when you want to grab a spin lock, when things like BBSSI exists. But NetBSD would need some serious rewriting to properly abstract locks and other things in a way that would allow the native VAX instructions to be possible to use.
I have a little hard time believing it's the CAS handling that is having a problem with large memories though. Why do you think it's there?
But it's been so long since I played with this I almost don't remember anything. Would need to go back down that rabbit hole from the start again if so.
Johnny
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