Re: [PATCH 1/2] sched,time: remove pointless divides from __acct_update_integrals

2016-01-29 Thread Rik van Riel
On 01/29/2016 10:36 PM, Frederic Weisbecker wrote: > On Sat, Jan 30, 2016 at 12:10:18AM +0100, Peter Zijlstra wrote: >> On Fri, Jan 29, 2016 at 05:22:59PM -0500, r...@redhat.com wrote: >>> From: Rik van Riel >>> >>> When running a microbenchmark calling an invalid syscall number >>> in a loop, on

Re: [PATCH 1/2] sched,time: remove pointless divides from __acct_update_integrals

2016-01-29 Thread Frederic Weisbecker
On Sat, Jan 30, 2016 at 12:10:18AM +0100, Peter Zijlstra wrote: > On Fri, Jan 29, 2016 at 05:22:59PM -0500, r...@redhat.com wrote: > > From: Rik van Riel > > > > When running a microbenchmark calling an invalid syscall number > > in a loop, on a nohz_full CPU, we spend a full 9% of our CPU > > ti

Re: [PATCH 1/2] sched,time: remove pointless divides from __acct_update_integrals

2016-01-29 Thread Peter Zijlstra
On Fri, Jan 29, 2016 at 05:22:59PM -0500, r...@redhat.com wrote: > From: Rik van Riel > > When running a microbenchmark calling an invalid syscall number > in a loop, on a nohz_full CPU, we spend a full 9% of our CPU > time in __acct_update_integrals. > > This function converts cputime_t to jiff

[PATCH 1/2] sched,time: remove pointless divides from __acct_update_integrals

2016-01-29 Thread riel
From: Rik van Riel When running a microbenchmark calling an invalid syscall number in a loop, on a nohz_full CPU, we spend a full 9% of our CPU time in __acct_update_integrals. This function converts cputime_t to jiffies, to a timeval, only to convert the timeval back to microseconds before disc