On Sun, Jan 11, 2009 at 09:42:30PM +0300, Yuri Tikhonov wrote: > >This patch adds support for 256KB pages on ppc44x-based boards. > >For simplification of implementation with 256KB pages we still assume >2-level paging. As a side effect this leads to wasting extra memory space >reserved for PTE tables: only 1/4 of pages allocated for PTEs are >actually used. But this may be an acceptable trade-off to achieve the >high performance we have with big PAGE_SIZEs in some applications (e.g. >RAID). > >Also with 256KB PAGE_SIZE we increase THREAD_SIZE up to 32KB to minimize >the risk of stack overflows in the cases of on-stack arrays, which size >depends on the page size (e.g. multipage BIOs, NTFS, etc.). > >With 256KB PAGE_SIZE we need to decrease the PKMAP_ORDER at least down >to 9, otherwise all high memory (2 ^ 10 * PAGE_SIZE == 256MB) we'll be >occupied by PKMAP addresses leaving no place for vmalloc. We do not >separate PKMAP_ORDER for 256K from 16K/64K PAGE_SIZE here; actually that >value of 10 in support for 16K/64K had been selected rather intuitively. >Thus now for all cases of PAGE_SIZE on ppc44x (including the default, 4KB, >one) we have 512 pages for PKMAP. > >Because ELF standard supports only page sizes up to 64K, then you should >use binutils later than 2.17.50.0.3 with '-zmax-page-size' set to 256K >for building applications, which are to be run with the 256KB-page sized >kernel. If using the older binutils, then you should patch them like follows: > >--- binutils/bfd/elf32-ppc.c.orig >+++ binutils/bfd/elf32-ppc.c > >-#define ELF_MAXPAGESIZE 0x10000 >+#define ELF_MAXPAGESIZE 0x40000 > >Signed-off-by: Yuri Tikhonov <y...@emcraft.com> >Signed-off-by: Ilya Yanok <ya...@emcraft.com>
Thanks. I particularly like the additional option you have to disable before 256K pages is an option. I'll do a bit of testing, and barring any unforeseen problems, I'll queue this up for 2.6.30. josh _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
