This of course causes problems for applications that try to use page protection to track updates or are relying on small granularity copy-on-write, or the like. Anything that uses our garbage collector in incremental mode will fit that description, though I don't believe there are currently many such applications. Checkpointing may be another similar issue, at least for some applications. Software DSM implementations would clearly be affected. I would guess that the trend is likely to be towards more of this in all three of those areas. I am not really arguing against this, since I don't have a good overview of how many customers are likely to be affected. I just want to make sure that both sides of the issue are considered. Hans > -----Original Message----- > From: linux-ia64-owner@xxxxxxxxxxxxxxx > [mailto:linux-ia64-owner@xxxxxxxxxxxxxxx] On Behalf Of Jack Steiner > Sent: Thursday, June 07, 2007 6:33 PM > To: Christoph Lameter > Cc: tony.luck@xxxxxxxxx; linux-ia64@xxxxxxxxxxxxxxx > Subject: Re: [IA64] Set default page size to 64k > > On Thu, Jun 07, 2007 at 06:05:46PM -0700, Christoph Lameter wrote: > > It seems that 16k page size causes Itanium processors to have > > significant TLB overhead when the working set is growing beyond 2M. > > Setting the page size to 64k reduces this problem. > > At one time, there were file system issues with 64K pages. I > _hope_ that these have been fixed. I'll cc Dave Chinner for > his 2 cents. > > Note that changing the IA64 default doesn't really help > customers - the distros also need to change. Changing the > default to 64K will help determine if there are any > additional issues that need to be fixed. > Distros will have more confidence in 64K if it's the default > in the community kernel. > > > > > > > > See the paper of the researchers at the TU Dresden on TLB issues: > > > http://www.cs.utah.edu/wmpi/2006/final-version/wmpi-posters-3-Juckelan > > d.pdf > > and my presentation > > > http://ftp.kernel.org/pub/linux/kernel/people/christoph/gelato > /gelato2007-tlb-tricks.pdf. > > > > SLUB can also take advantage of the larger page sizes. A kernel > > compile is already ~5-10% faster with 16k. This will increase the > > speed even more. It will also increase the effectiveness of slab > > reclaim because more objects can be processed with a single > acquisition of the dcache or inode lock. > > > > We at SGI have begun to see livelocks because of too much > activity on > > various locks. This is simply because there are too many > pages in the > > system which require frequent taking of locks. Going to 64k > page size > > will reduce the frequency of taking locks by a factor of 4. > > > > IA64 systems typically have very large memory capacities. > Going to 64k > > will increase the memory footprint but I think we are > willling to make > > that sacrifice for the speed the larger page size brings us. > > > > Signed-off-by: Christoph Lameter <clameter@xxxxxxx> > > > > Index: slub/arch/ia64/Kconfig > > =================================================================== > > --- slub.orig/arch/ia64/Kconfig 2007-05-31 > 11:44:50.000000000 -0700 > > +++ slub/arch/ia64/Kconfig 2007-06-07 17:39:02.000000000 -0700 > > @@ -168,7 +168,7 @@ endchoice > > > > choice > > prompt "Kernel page size" > > - default IA64_PAGE_SIZE_16KB > > + default IA64_PAGE_SIZE_64KB > > > > config IA64_PAGE_SIZE_4KB > > bool "4KB" > > Index: slub/arch/ia64/configs/sn2_defconfig > > =================================================================== > > --- slub.orig/arch/ia64/configs/sn2_defconfig > 2007-06-07 17:41:22.000000000 -0700 > > +++ slub/arch/ia64/configs/sn2_defconfig 2007-06-07 > 17:56:34.000000000 -0700 > > @@ -110,8 +110,8 @@ CONFIG_IA64_SGI_SN2=y CONFIG_MCKINLEY=y # > > CONFIG_IA64_PAGE_SIZE_4KB is not set # > CONFIG_IA64_PAGE_SIZE_8KB is > > not set -CONFIG_IA64_PAGE_SIZE_16KB=y -# > CONFIG_IA64_PAGE_SIZE_64KB is > > not set > > +# CONFIG_IA64_PAGE_SIZE_16KB is not set > CONFIG_IA64_PAGE_SIZE_64KB=y > > # CONFIG_PGTABLE_3 is not set > > CONFIG_PGTABLE_4=y > > # CONFIG_HZ_100 is not set > > Index: slub/arch/ia64/configs/gensparse_defconfig > > =================================================================== > > --- slub.orig/arch/ia64/configs/gensparse_defconfig > 2007-06-07 17:56:54.000000000 -0700 > > +++ slub/arch/ia64/configs/gensparse_defconfig > 2007-06-07 17:57:24.000000000 -0700 > > @@ -101,8 +101,8 @@ CONFIG_IA64_GENERIC=y CONFIG_MCKINLEY=y # > > CONFIG_IA64_PAGE_SIZE_4KB is not set # > CONFIG_IA64_PAGE_SIZE_8KB is > > not set -CONFIG_IA64_PAGE_SIZE_16KB=y -# > CONFIG_IA64_PAGE_SIZE_64KB is > > not set > > +# CONFIG_IA64_PAGE_SIZE_16KB is not set > CONFIG_IA64_PAGE_SIZE_64KB=y > > CONFIG_PGTABLE_3=y > > # CONFIG_PGTABLE_4 is not set > > # CONFIG_HZ_100 is not set > > - > > To unsubscribe from this list: send the line "unsubscribe > linux-ia64" > > in the body of a message to majordomo@xxxxxxxxxxxxxxx More > majordomo > > info at http://vger.kernel.org/majordomo-info.html > > -- > Thanks > > Jack Steiner (steiner@xxxxxxx) 651-683-5302 > Principal Engineer SGI - Silicon Graphics, Inc. > > > - > To unsubscribe from this list: send the line "unsubscribe > linux-ia64" in the body of a message to > majordomo@xxxxxxxxxxxxxxx More majordomo info at > http://vger.kernel.org/majordomo-info.html > - To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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