On 08/30/2016 11:24 AM, Aaron Lu wrote: > On 08/30/2016 12:44 PM, Anshuman Khandual wrote: >> > On 08/30/2016 09:09 AM, Andrew Morton wrote: >>> >> On Tue, 30 Aug 2016 11:09:15 +0800 Aaron Lu <aaron.lu@xxxxxxxxx> wrote: >>> >> >>>>>> >>>>> Case used for test on Haswell EP: >>>>>> >>>>> usemem -n 72 --readonly -j 0x200000 100G >>>>>> >>>>> Which spawns 72 processes and each will mmap 100G anonymous space and >>>>>> >>>>> then do read only access to that space sequentially with a step of 2MB. >>>>>> >>>>> >>>>>> >>>>> perf report for base commit: >>>>>> >>>>> 54.03% usemem [kernel.kallsyms] [k] get_huge_zero_page >>>>>> >>>>> perf report for this commit: >>>>>> >>>>> 0.11% usemem [kernel.kallsyms] [k] mm_get_huge_zero_page >>>>> >>>> >>>>> >>>> Does this mean that overall usemem runtime halved? >>>> >>> >>>> >>> Sorry for the confusion, the above line is extracted from perf report. >>>> >>> It shows the percent of CPU cycles executed in a specific function. >>>> >>> >>>> >>> The above two perf lines are used to show get_huge_zero_page doesn't >>>> >>> consume that much CPU cycles after applying the patch. >>>> >>> >>>>> >>>> >>>>> >>>> Do we have any numbers for something which is more real-wordly? >>>> >>> >>>> >>> Unfortunately, no real world numbers. >>>> >>> >>>> >>> We think the global atomic counter could be an issue for performance >>>> >>> so I'm trying to solve the problem. >>> >> >>> >> So, umm, we don't actually know if the patch is useful to anyone? >> > >> > On a POWER system it improves the CPU consumption of the above mentioned >> > function a little bit. Dont think its going to improve actual throughput >> > of the workload substantially. >> > >> > 0.07% usemem [kernel.vmlinux] [k] mm_get_huge_zero_page > I guess this is the base commit? But there shouldn't be the new > mm_get_huge_zero_page symbol before this patch. A typo perhaps? Yeah, sorry about that. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>