Messages in this thread | | | Subject | Re: [PATCH 1/2] Define new percpu interface for shared data -- version 3 | From | Martin Schwidefsky <> | Date | Thu, 24 May 2007 11:03:56 +0200 |
| |
On Wed, 2007-05-23 at 11:57 -0700, Ravikiran G Thirumalai wrote: > > >OK, but could we please have a concise description of the impact > > >of these changes on kernel memory footprint? Increase or decrease? > > >And by approximately how much? > > > > Depending on how linker places percpu data, the patches could > > increase or decrease percpu section size. Data from 2.6.21-rc7-mm2: > > > > On x86 SMP, the section size is increased from 0x7768 to 0x790c. > > 1.3% increase. > > > > On X86-64 SMP, the size is decreased from 0x72d0 to 0x6540. > > 11.8% decrease. > > > > On X86-64 VSMP, the size is increased from 0x72d0 to 0x8340. > > 14.3% increase. > > > > On IA64 SMP, the size is decreased from 0x8370 to 0x7fc0. > > 2.8% decrease. > > Has there been any measurable benefit yet due to tail padding? > It would also be interesting to check the wastage/savings on another > large > cache architecture like S390 (which has a 256 byte cache line)
Current git with the patches applied and the default configuration for s390 decreases the section size fof .data.percpu from 0x3e50 to 0x3e00. 0.5% decrease.
-- blue skies, Martin.
"Reality continues to ruin my life." - Calvin.
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |