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Message-ID: <20231205102302.58434-1-jalliste@amazon.com>
Date: Tue, 5 Dec 2023 10:23:02 +0000
From: Jack Allister <jalliste@...zon.com>
To: <dave.hansen@...el.com>
CC: <bp@...en8.de>, <dave.hansen@...ux.intel.com>,
<hdegoede@...hat.com>, <hpa@...or.com>, <jalliste@...zon.com>,
<juew@...zon.com>, <len.brown@...el.com>,
<linux-kernel@...r.kernel.org>, <mingo@...hat.com>,
<pdurrant@...zon.com>, <peterz@...radead.org>,
<rafael.j.wysocki@...el.com>, <rafael@...nel.org>,
<tglx@...utronix.de>, <usama.arif@...edance.com>, <x86@...nel.org>
Subject: Re: [PATCH] x86: intel_epb: Add earlyparam option to keep bias at performance
> 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?
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