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Diffstat (limited to 'docs/man/xm.pod.1')
| -rw-r--r-- | docs/man/xm.pod.1 | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/docs/man/xm.pod.1 b/docs/man/xm.pod.1 index 7c4ef851b0..4d47388eb2 100644 --- a/docs/man/xm.pod.1 +++ b/docs/man/xm.pod.1 @@ -767,6 +767,19 @@ is expressed in percentage of one physical CPU: 100 is 1 physical CPU, 50 is half a CPU, 400 is 4 CPUs, etc. The default, 0, means there is no upper cap. +NB: Many systems have features that will scale down the computing +power of a cpu that is not 100% utilized. This can be in the +operating system, but can also sometimes be below the operating system +in the BIOS. If you set a cap such that individual cores are running +at less than 100%, this may have an impact on the performance of your +workload over and above the impact of the cap. For example, if your +processor runs at 2GHz, and you cap a vm at 50%, the power management +system may also reduce the clock speed to 1GHz; the effect will be +that your VM gets 25% of the available power (50% of 1GHz) rather than +50% (50% of 2GHz). If you are not getting the performance you expect, +look at performance and cpufreq options in your operating system and +your BIOS. + =back =item B<sched-sedf> I<period> I<slice> I<latency-hint> I<extratime> I<weight> |