Re: [Xen-devel][PATCH] Revert Jan's patch (c/s 18879) since now itcanbe achieved by xenpm tool now

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 23/12/2008 02:29, "Liu, Jinsong" <jinsong.liu@xxxxxxxxx> wrote:

> Some cpufreq governor may fail at init stage, i.e. performance governor cannot
> start at some platform with hardware flaw.
> In this case, if user select performance gov at cmdline, governor init will
> fail and then whole cpufreq init will fail, xen will have no cpufreq then.
> 
> Our idea is, first step cpufreq logic select a 'safe' governor as default,
> say, userspace governor. It will never fail, since it keep cpu freq just like
> it didn't work at init stage, so will not have any influence to perfromance,
> power, ..., etc.
> Second step, user can change to any other governor as he like, if fail,
> cpufreq logic can gracefully back to the 'old-safe-governor'.
> This way at least xen can ensure cpufreq logic successful, and safe change
> between different governors.

Two thoughts: Firstly, the user should be wary of such behaviour if they
have explicitly selected a governor on the command line. Secondly, if it is
appropriate to have cpufreq always on, why not hardcode a safe governor as a
fallback?

 -- Keir



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