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From:   Jack Allister <jalliste@amazon.com>
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Subject: Re: [PATCH] x86: intel_epb: Add earlyparam option to keep bias at performance
Date:   Tue, 5 Dec 2023 10:23:02 +0000
Message-ID: <20231205102302.58434-1-jalliste@amazon.com>
In-Reply-To: <c1e8e8cb-f792-4dcc-a72f-fbebe4476a1b@intel.com>
References: <c1e8e8cb-f792-4dcc-a72f-fbebe4476a1b@intel.com>
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> This is fundamentally a hack.

I do not totally agree that this is a hack, the setting of it to the
ENERGY_PERF_BIAS_NORMAL is an equivalent workaround which is used for
systems where the platform firmware has not configured it as expected
for laptops etc. and that is already present.

> It sounds like you want the system default to be at
> ENERGY_PERF_BIAS_PERFORMANCE.  You also mentioned that this was done "on
> kernel boot".  How did you do that, exactly?  Shouldn't that "on kernel
> boot" action be reflected over here rather than introducing another
> command-line parameter?

As Paul has mentioned, we perform live-updates of the host kernel running
on servers. This is done while virtual machines are still running so that
there is no perceived downtime for the guest/customer. This requires a
kexec into the new kernel and there are specific areas such as PCI device
enumeration which can take a substantial amount of time in it's current
form and can be perceived as downtime while the kernel is loading.

> Shouldn't that "on kernel
> boot" action be reflected over here rather than introducing another
> command-line parameter?

A kernel parameter may not be the most elegant solution, would a proposal
for a kernel build configuration be a bit more suitable?