Hi Felix, > > I remember the discussion very good. I am complaining that Red Hat is > > the technology leader now. Sun had half a year to deal with the > > problem. Why is it so difficult to change the number from 21 to 64 as > > proposed in the previous discussion? > > Fair enough. I had a look at the work in progress and it looks like there > are a fair number of changes required (not huge, but more than you'd hope > given sparc has large ncpu and much code is common). Most work has been > in the multiboot and acpi areas by the looks of things. There has been > activity within the workspace within the last week so it's not been dropped > on the floor. I imagine the responsible engineer may followup here.
I have a wad with changes to raise NCPU to 32 on 32-bit kernels and 64 on 64-bit kernels. The reason why it is not in the gate yet is because Solaris kernel sets max_ncpus variable to NCPU and there are quite a few memory allocations that happen early on boot that are based on that number. For example, kmem itself uses max_ncpus to allocate per-CPU caches early on boot. What we need to do is to set max_ncpus very early on boot to the actual number of processors installed on the system we're booting on. On sparc we get that number from the OBP, but on x86/amd64 we have to parse one specific APIC table to find it. Unfortunately, our acpi driver gets loaded pretty late in the boot process, so we've tried to make multiboot or the kernel itself (but very early) to scan that APIC table. We're still working on this tricky part, but I would like to propose an interim solution to be putback soon. Basically, it could raise NCU to 32/64 but limit max_ncpus to 16 by default. What this means is that one will be able to boot with 16 processors w/o any tuning, but if Solaris needs to boot on a system with more than 16 processors, a simple tuning of boot_max_ncpus in /etc/system will be required. I don't think there any systems out there with more than 16 but less than 22 CPUs so it would be a pretty low risk change. I'd like to hear what people who care about this stuff think. Also, if there is anyone interested in helping us with getting acpi parsing code in multiboot, please let me know. I can also publish a webrev with our current set of changes if anyone wants to see what was done already. We're also discussing this change with folks working on Xen since they're planning to get rid of multiboot. - Andrei _______________________________________________ opensolaris-discuss mailing list [email protected]
