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Date: Mon, 12 Sep 2022 15:07:35 +0200
Message-Id: <CMUG2DUUFPDZ.21TDKCEIN8UCS@sumire>
Subject: Re: performance drop with alpine linux upgrade
From: "alice" <alice@ayaya.dev>
To: "Riccardo Mottola" <riccardo.mottola@libero.it>, "alpine-user"
 <alpine-user@lists.alpinelinux.org>
References: <196e1b55-ade9-8a4b-889b-006fef7f63c1@libero.it>
 <CMUCC7OZ4Y9K.10UWLB8RC8NP8@sumire>
 <9cb23b83-bf70-dd44-6249-a69e30e6f3e0@libero.it>
In-Reply-To: <9cb23b83-bf70-dd44-6249-a69e30e6f3e0@libero.it>

On Mon Sep 12, 2022 at 2:59 PM CEST, Riccardo Mottola wrote:
> Hello Alice,
>
>
> alice wrote:
> > On Mon Sep 12, 2022 at 10:47 AM CEST, Riccardo Mottola wrote:
> > you should monitor the frequency during that- it probably goes down/up
> > as the fans do
>
> cpuinfo gives always the same frequency
> >> I can think of two causes, from my past experience with other systems:
> >> - disabled caches
> > i don't think a kernel update would change this, either
> >> - CPU not runnig at full speed
> >>
> >> In the BIOS I checked and CPU and L2 caches are enabled (small in this
> >> crippled CPU anyway).
> >> Could some APM/ACPI lower the cpu speed until I rise it withsome gover=
nor?
> > you can check the governors with:
> > cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
>
> my cpu9 does not have cpufreq, either it is not supported at all on this
> old CPU model or something is not detected?
> That would make me guess however that it runs at the speed shown in
> cpuinfo, 2.2GHz.
aha, i thought it was just a tad newer :) apologies. yeah, things from
that era don't usually change clocks that much.
>
> also:
>
> cervino:~# cpufreq-info
> cpufrequtils 008: cpufreq-info (C) Dominik Brodowski 2004-2009
> Report errors and bugs to cpufreq@vger.kernel.org, please.
> analyzing CPU 0:
>
> >
> > but i don't think even being stuck on "powersave" or something would do
> > that.. strange
>
> No, I would, at the opposite, suppose it would be stuck to the frequency
> reported in cpuinfo, that is, the maximum
>
> >
> > this sounds like some weird kernel regression in 5.15, if anything
>
> strange indeed
>
> 5.15.64-0-lts #1-Alpine SMP Mon, 05 Sep 2022 08:02:49 +0000 i686 Linux
>
>
> in dmesg I see:
> [=C2=A0=C2=A0=C2=A0 1.605776] intel_pstate: CPU model not supported
>
>
> but I don't know if this is relevant, this CPU is based on netburst
> architecture. I think that back then, few cpu scaling methods where
> available. Original speedstep and perhaps p4_clockmod - where the clock
> doesn't really change?
maybe there's a chance that if intel_pstate loads first it blocks the
others? (just guessing). both of the others are also available as
modules, maybe something funny happens with pstate. perhaps
modprobe.blacklist=3Dintel_pstate does something (or similar things in
that vein)
>
> I cannot identify this CPU here:
> https://en.wikipedia.org/wiki/List_of_Intel_Celeron_processors#Netburst_b=
ased_Celerons
>
> since 2.2Ghz appears to have 128K cache. It could be this one:
> https://ark.intel.com/content/www/us/en/ark/products/27318/mobile-intel-c=
eleron-processor-2-20-ghz-256k-cache-400-mhz-fsb.html
>
> still i don't think too much relevant to have the exact detail.
>
>
> > add mitigations=3Doff to the kernel cmdline, via whatever booting setup
> > you have. usual warnings/caveats apply, but there you go. i doubt they
> > would be that impactful though..
>
> I doubt too, on more modern CPUs I have found an impact of 1% to 10%
> usually... but maybe on this old cache-limited CPU?
>
> I have syslinux, I don't know hot do add that option to
> |/etc/update-extlinux.conf|, but I will add it manually for a boot and
> test the difference.
the default_kernel_opts line can have it
>
> Riccardo