Messages in this thread | | | Date | Thu, 7 Jul 2022 09:37:57 -0500 | Subject | Re: [PATCH 5/8] arm64: Create cache sysfs directory without ACPI PPTT for hardware prefetch control | From | Jeremy Linton <> |
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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.
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