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Diffstat (limited to 'docs/man/xl.cfg.pod.5')
| -rw-r--r-- | docs/man/xl.cfg.pod.5 | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/docs/man/xl.cfg.pod.5 b/docs/man/xl.cfg.pod.5 index b7d64a6d7d..069b73ff60 100644 --- a/docs/man/xl.cfg.pod.5 +++ b/docs/man/xl.cfg.pod.5 @@ -153,6 +153,19 @@ The cap is expressed in percentage of one physical CPU: The default, 0, means there is no upper cap. Honoured by the credit and credit2 schedulers. +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. + =item B<period=NANOSECONDS> The normal EDF scheduling usage in nanoseconds. This means every period |