On Tue, 18 Nov 2008 10:13:16 +1100 Benjamin Herrenschmidt <[EMAIL PROTECTED]> wrote:
> > > Well, it's not unacceptable on good CPU's with 4kB blocks (just an 8-entry > > array), but as you say: > > > > > On PPC64 I'm told that the page size is 64K, which makes the above equal > > > to: 64K / 512 = 128 multiply that by 8 byte words, we have 1024 bytes. > > > > Yeah. Not good. I think 64kB pages are insane. In fact, I think 32kB > > pages are insane, and 16kB pages are borderline. I've told people so. > > > > The ppc people run databases, and they don't care about sane people > > telling them the big pages suck. > > Hehe :-) > > Guess who is pushing for larger page sizes nowadays ? Embedded > people :-) In fact, we have patches submited on the list to offer the > option for ... 256K pages on some 44x embedded CPUs :-) For clarification, that workload is very precise. Namely embedded 44x CPUs used in RAID cards. I'm not entirely convinced bringing 256K pages into mainline is a good thing yet anyway. 64K pages, while seemingly insane for embedded boards that typically have less than 512 MiB of DRAM, help for a bit larger set of workloads. As a KVM host is the primary winner at the moment. But given the small number of TLB entries on these CPUs, it can pay off elsewhere as well. josh _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
