Messages in this thread | | | From | "Rafael J. Wysocki" <> | Date | Mon, 28 Nov 2016 23:22:50 +0100 | Subject | Re: [PATCH v4 1/2] idle: add support for tasks that inject idle |
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On Mon, Nov 28, 2016 at 10:46 PM, Jacob Pan <jacob.jun.pan@linux.intel.com> wrote: > On Mon, 28 Nov 2016 22:39:07 +0100 > "Rafael J. Wysocki" <rafael@kernel.org> wrote: > >> On Mon, Nov 28, 2016 at 10:33 PM, Jacob Pan >> <jacob.jun.pan@linux.intel.com> wrote: >> > From: Peter Zijlstra <peterz@infradead.org> >> > >> > Idle injection drivers such as Intel powerclamp and ACPI PAD >> > drivers use realtime tasks to take control of CPU then inject idle. >> > There are two issues with this approach: >> > >> > 1. Low efficiency: injected idle task is treated as busy so sched >> > ticks do not stop during injected idle period, the result of these >> > unwanted wakeups can be ~20% loss in power savings. >> > >> > 2. Idle accounting: injected idle time is presented to user as >> > busy. >> > >> > This patch addresses the issues by introducing a new PF_IDLE flag >> > which allows any given task to be treated as idle task while the >> > flag is set. Therefore, idle injection tasks can run through the >> > normal flow of NOHZ idle enter/exit to get the correct accounting >> > as well as tick stop when possible. >> > >> > The implication is that idle task is then no longer limited to PID >> > == 0. >> > >> > Acked-by: Ingo Molnar <mingo@kernel.org> >> > Signed-off-by: Peter Zijlstra <peterz@infradead.org> >> > Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com> >> >> Have you made any changes to the original Peter's patch, or is this >> just a resend of that? > No changes made to Peter's patch. I just rebased to v4.9-rc7 and tested > it.
OK, thanks!
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