[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Thu, 7 Jul 2022 09:37:57 -0500
From: Jeremy Linton <jeremy.linton@....com>
To: "tarumizu.kohei@...itsu.com" <tarumizu.kohei@...itsu.com>,
'Sudeep Holla' <sudeep.holla@....com>
Cc: "catalin.marinas@....com" <catalin.marinas@....com>,
"will@...nel.org" <will@...nel.org>,
"tglx@...utronix.de" <tglx@...utronix.de>,
"mingo@...hat.com" <mingo@...hat.com>,
"bp@...en8.de" <bp@...en8.de>,
"dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
"x86@...nel.org" <x86@...nel.org>, "hpa@...or.com" <hpa@...or.com>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 5/8] arm64: Create cache sysfs directory without ACPI PPTT
for hardware prefetch control
Hi,
On 2/1/22 05:56, tarumizu.kohei@...itsu.com wrote:
>> I am assuming this is ACPI enabled system.
>
> Yes, it is ACPI enabled system.
>
>> This looks bit hacky in my opinion. Before I explore better way of adding it, I would
>> like to check if you have explored ways to add PPTT reading these registers from
>> UEFI/EDK2 as PPTT has other topology information which you will need anyways.
>> That would simplify handling of these cacheinfo sysfs in the kernel. Let me know
>> what are your thoughts ?
>
> The latest firmware of ARM64 machine, FX700 with the A64FX processor
> does not support PPTT.
> I think adding PPTT is the best way to generate cacheinfo sysfs.
> However, it is difficult to modify the firmware to add PPTT, so
> it is not clear when it will be possible.
> Therefore, I would like to implement the function in the kernel on
> the condition that firmware does not support PPTT.
As a bit of a late comment here, I assume you tried injecting the PPTT
via the initrd (directions in
admin-guide/acpi/initrd_table_override.txt) then? That is one of the
usual kernel workarounds for broken/missing ACPI tables.
As mentioned above, besides not providing appropriate topology
information to userspace, not having the PPTT is also possibly causing
suboptimal scheduling decisions in the kernel itself.
Powered by blists - more mailing lists