On (04/01/08 00:34), Arnd Bergmann didst pronounce: > On Thursday 03 January 2008, Jon Tollefson wrote: > > Paul, please include this in 2.6.25 if there are no objections. > > No objections to this version from me, just questions. > > > This patch adds the hugepagesz boot-time parameter for ppc64. It lets > > one pick the size for huge pages. The choices available are 64K and 16M > > when the base page size is 4k. It defaults to 16M (previously the only > > only choice) if nothing or an invalid choice is specified. > > We started discussing this in v1, but the discussion got sidetracked: > Is there a technical reason why you don't also allow 1M pages, which > may be useful in certain scenarios? >
I cannot see why not although the ideal would be that the necessary information to support the pagesize would be provided by the firmware instead of hard-coded values. > On the Cell/B.E. platforms (IBM/Mercury blades, Toshiba Celleb, PS3), the > second large page size is an option that can be set in a HID SPR > to either 64KB or 1MB. Unfortunately, we can't do these two simultaneously, > but the firmware can change the default and put it into the device tree, > or you could have the kernel override the firmware settings. > > Going a lot further, do you have plans for a fully dynamic hugepage size, > e.g. using a mount option for hugetlbfs? A mount option for hugetlbfs to select a hugepage size is a long-term goal. However, a lot of changes are required to support such a thing. Selecting the hugepage size at boot-time is a reasonable starting point and one that might be usable with some additional work by x86-64 on AMD processors supporting 1GiB pages. > I can see that as rather useful, > but at the same time it's probably much more complicated than the boot time > option. > Not probably at all. It is *certainly* much more complicated than the boot-time option :) -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
