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-Juckeland.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 <[EMAIL PROTECTED]> > > 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 [EMAIL PROTECTED] > More majordomo info at http://vger.kernel.org/majordomo-info.html -- Thanks Jack Steiner ([EMAIL PROTECTED]) 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 [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
