On Wed, 10 Feb 2016, [email protected] wrote: > (v6: make VIRT_CPU_ACCOUNTING_GEN jiffy granularity) > > Running with nohz_full introduces a fair amount of overhead. > Specifically, various things that are usually done from the > timer interrupt are now done at syscall, irq, and guest > entry and exit times. > > However, some of the code that is called every single time > has only ever worked at jiffy resolution. The code in > __acct_update_integrals was also doing some unnecessary > calculations. > > Getting rid of the unnecessary calculations, without > changing any of the functionality in __acct_update_integrals > gets us about an 11% win. > > Not calling the time statistics updating code more than > once per jiffy, like is done on housekeeping CPUs and on > all the CPUs of a non-nohz_full system, shaves off a > further 30%.
Reviewed-by: Thomas Gleixner <[email protected]>
