From: Sudeep Holla <sudeep.holla@arm.com>
To: Jeremy Linton <jeremy.linton@arm.com>
Cc: "tarumizu.kohei@fujitsu.com" <tarumizu.kohei@fujitsu.com>,
"catalin.marinas@arm.com" <catalin.marinas@arm.com>,
Sudeep Holla <sudeep.holla@arm.com>,
"will@kernel.org" <will@kernel.org>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"mingo@redhat.com" <mingo@redhat.com>,
"bp@alien8.de" <bp@alien8.de>,
"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
"x86@kernel.org" <x86@kernel.org>,
"hpa@zytor.com" <hpa@zytor.com>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 5/8] arm64: Create cache sysfs directory without ACPI PPTT for hardware prefetch control
Date: Thu, 7 Jul 2022 15:44:04 +0100 [thread overview]
Message-ID: <20220707144404.pm3qtgfo6fsik77d@bogus> (raw)
In-Reply-To: <4b99cf3c-f40b-cba7-2fa2-b6b311859776@arm.com>
On Thu, Jul 07, 2022 at 09:37:57AM -0500, Jeremy Linton wrote:
> Hi,
>
> On 2/1/22 05:56, tarumizu.kohei@fujitsu.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.
>
Thanks a lot for the suggestion Jeremy. For some reason, I missed to follow
up on this after my initial response. Anyways I agree injecting PPTT via
initrd is a good compromise on systems that are shipped without or broken
PPTT. I have tested that to be fully functional on v5.19-rc* on one of
the servers shipped with broken PPTT.
--
Regards,
Sudeep
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next prev parent reply other threads:[~2022-07-07 14:46 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-25 7:14 [PATCH 0/8] Add hardware prefetch control driver for arm64 and x86 Kohei Tarumizu
2022-01-25 7:14 ` [PATCH 1/8] drivers: base: Add hardware prefetch control core driver Kohei Tarumizu
2022-01-25 7:14 ` [PATCH 2/8] drivers: base: Add Kconfig/Makefile to build " Kohei Tarumizu
2022-01-25 7:14 ` [PATCH 3/8] arm64: Add hardware prefetch control support for ARM64 Kohei Tarumizu
2022-01-25 7:14 ` [PATCH 4/8] arm64: Add Kconfig/Makefile to build hardware prefetch control driver Kohei Tarumizu
2022-01-29 17:03 ` Randy Dunlap
2022-02-01 12:04 ` tarumizu.kohei
2022-01-25 7:14 ` [PATCH 5/8] arm64: Create cache sysfs directory without ACPI PPTT for hardware prefetch control Kohei Tarumizu
2022-01-26 10:36 ` Sudeep Holla
2022-02-01 11:56 ` tarumizu.kohei
2022-07-07 14:37 ` Jeremy Linton
2022-07-07 14:44 ` Sudeep Holla [this message]
2022-07-08 10:21 ` tarumizu.kohei
2022-01-25 7:14 ` [PATCH 6/8] x86: Add hardware prefetch control support for x86 Kohei Tarumizu
2022-01-25 7:14 ` [PATCH 7/8] x86: Add Kconfig/Makefile to build hardware prefetch control driver Kohei Tarumizu
2022-01-25 7:14 ` [PATCH 8/8] docs: ABI: Add sysfs documentation interface of " Kohei Tarumizu
2022-01-25 15:12 ` [PATCH 0/8] Add hardware prefetch control driver for arm64 and x86 Dave Hansen
2022-01-26 9:24 ` tarumizu.kohei
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