Hi all,
Could a common solution be provided for RT thread requirement or other
latency sensitive applications to temporarily disable power management features
to reduce latency? Currently cpu power management runs into this issue, I think
future memory power management may also run into the same situation. One of our
memory power saving prototype project has this requirement too. So how about a
common mechanism like kprement to temparorily disable power management features?
bugzilla-daemon at defect.opensolaris.org <> wrote:
> http://defect.opensolaris.org/bz/show_bug.cgi?id=3098
>
> Summary: Deep C-State must meet Real Time thread
> requirements Classification: Development
> Product: power-mgmt
> Version: unspecified
> Platform: Other
> OS/Version: Solaris
> Status: NEW
> Severity: minor
> Priority: P3
> Component: c-state
> AssignedTo: bill.holler at sun.com
> ReportedBy: bill.holler at sun.com
> CC: tesla-dev at opensolaris.org
> Estimated Hours: 0.0
>
>
> Deep C-state support will add a wakeup latency to idle CPUs.
> This latency must not be so large it breaks RT requirements.
>
> What is the RT requirement?
>
> I might be possible processor performance has increased enough since
> any RT requirement was made that even CPUs comming out of Deep
> C-state meet the requirement?
>
>
> Multiple possible solutions exist.
> 1. Disable Deep C-states when the RT scheduling class is loaded.
> 2. Schedule a CPU to wakeup from Deep C-state some time ahead of when
> a RT callout will expire.
> 3. Schedule RT threads on groups of CPUs that do not enter Deep
> C-states while other CPU groups are allowed to.
