On Friday 04 June 2010 1:58:13 pm Alan Cox wrote: > Matthew D Fleming wrote: > > On Fri, Jun 04, 2010 at 08:20:49AM -0400, John Baldwin wrote: > > > >> Hmmm, I would just try increasing NKPT then. You might have to poke > >> around in sys/amd64 to see what the default size is and how to tune > >> it. > >> > > > > When Isilon did the stable/7 merge and amd64 default NKPT changed from > > 240 to 32 amd64 started having weird pmap issues during boot. At panic > > time the stack wasn't very useful, and I didn't finish debugging the > > issue since eventually I just had to get something working. We just > > reverted NKPT to 240 and it worked for us. I didn't see an anything in > > optsions.amd64 so I hard-coded it in amd64/include/pmap.h. > > > > Supposedly amd64 can deal with a small NKPT and grow dynamically, but it > > didn't seem to work for us. :-( Perhaps when we do the next merge > > project I'll have a few days to devote to debugging the root cause. > > > > NKPT controls the number of page table pages that are initially > allocated at the bottom of the top 2GB of the kernel address space. > However, the vast majority of the kernel address space, 510GB in FreeBSD > >=7.3, is below these page table pages. The page table pages for this > region are dynamically allocated as needed. > > If you're booting a kernel and modules greater than 64GB in size, then I > can certainly see why you would need to increase NKPT.
64GB seems like a lot of address space, I would not expect that to be completely used by kernel and modules. I think earlier in the thread someone said they had problems with a "mere" 295MB mfsroot. > John, is there some way to know at boot time how big the kernel and > modules were? Then, we could probably eliminate NKPT. I think the loader knows, so it could pass that info to the kernel. -- John Baldwin _______________________________________________ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to "freebsd-stable-unsubscr...@freebsd.org"
