Re: [question] sched: idle_avg and migration latency

2013-12-10 Thread Mike Galbraith
On Tue, 2013-12-10 at 19:31 +0100, Daniel Lezcano wrote: > I think I am a bit puzzled with the 'idle_avg' name. I am guessing the > semantic of this variable is "how long this cpu has been idle". Average distance between idles. > The idle duration, with the no_hz, could be long, several seconds

Re: [question] sched: idle_avg and migration latency

2013-12-10 Thread Alex Shi
On 12/11/2013 02:31 AM, Daniel Lezcano wrote: >> >> That has changed a little recently. I originally slammed avg_idle >> itself straight to max to ensure that a bursty load would idle balance, >> and not use stale data. If you start cross core switching at high >> frequency, you'll still shut idl

Re: [question] sched: idle_avg and migration latency

2013-12-10 Thread Daniel Lezcano
On 12/10/2013 04:20 PM, Alex Shi wrote: CC to MikeG, he written this part. :) I try to explain sth I know. I am sorry if my understanding incorrect. On 12/10/2013 07:30 PM, Daniel Lezcano wrote: Hi All, I am trying to understand how is computed the idle_avg and how it is used regarding the mi

Re: [question] sched: idle_avg and migration latency

2013-12-10 Thread Daniel Lezcano
On 12/10/2013 04:11 PM, Mike Galbraith wrote: On Tue, 2013-12-10 at 12:30 +0100, Daniel Lezcano wrote: Hi All, I am trying to understand how is computed the idle_avg and how it is used regarding the migration latency. 1. What is the sysctl_sched_migration_cost value ? It is initialized to 5000

Re: [question] sched: idle_avg and migration latency

2013-12-10 Thread Alex Shi
CC to MikeG, he written this part. :) I try to explain sth I know. I am sorry if my understanding incorrect. On 12/10/2013 07:30 PM, Daniel Lezcano wrote: > > Hi All, > > I am trying to understand how is computed the idle_avg and how it is > used regarding the migration latency. > > 1. What is

Re: [question] sched: idle_avg and migration latency

2013-12-10 Thread Mike Galbraith
On Tue, 2013-12-10 at 12:30 +0100, Daniel Lezcano wrote: > Hi All, > > I am trying to understand how is computed the idle_avg and how it is > used regarding the migration latency. > > 1. What is the sysctl_sched_migration_cost value ? It is initialized to > 50UL. Is it an arbitrarily chose

[question] sched: idle_avg and migration latency

2013-12-10 Thread Daniel Lezcano
Hi All, I am trying to understand how is computed the idle_avg and how it is used regarding the migration latency. 1. What is the sysctl_sched_migration_cost value ? It is initialized to 50UL. Is it an arbitrarily chosen value ? Could it change depending on the hardware performances ?