Messages in this thread | | | Date | Tue, 2 Jun 2009 19:47:37 +0530 | From | Rabin Vincent <> | Subject | Re: [PATCH] sched: sched_clock() clocksource handling. |
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On Tue, Jun 02, 2009 at 04:17:18PM +0900, Paul Mundt wrote: > sched: sched_clock() clocksource handling. > > There are presently a number of issues and limitations with how the > clocksource and sched_clock() interaction works today. Configurations > tend to be grouped in to one of the following: > > - Platform provides a clocksource unsuitable for sched_clock() > and prefers to use the generic jiffies-backed implementation. > > - Platform provides its own clocksource and sched_clock() that > wraps in to it. > > - Platform uses a generic clocksource (ie, drivers/clocksource/) > combined with the generic jiffies-backed sched_clock(). > > - Platform supports multiple sched_clock()-capable clocksources. > > This patch adds a new CLOCK_SOURCE_USE_FOR_SCHED_CLOCK flag to address > these issues, which can be set for any sched_clock()-capable clocksource. > > The generic sched_clock() implementation is likewise switched over to > always read from a designated sched_clocksource, which is default > initialized to the jiffies clocksource and updated based on the > availability of CLOCK_SOURCE_USE_FOR_SCHED_CLOCK sources. As this uses > the generic cyc2ns() logic on the clocksource ->read(), most of the > platform-specific sched_clock() implementations can subsequently be > killed off.
80ea3bac3a47bc73efa334d0dd57099d0ff14216 ("ARM: OMAP: sched_clock() corrected") seems to have switched omap from cyc2ns() to an open coded calculation based on mult_orig because cyc2ns() uses the NTP-adjusted mult instead. Does that apply here or is that change incorrect?
Rabin
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