From: Will Deacon <will@kernel.org>
To: catalin.marinas@arm.com, rafael@kernel.org, lenb@kernel.org,
saket.dumbre@intel.com, beata.michalska@arm.com,
zhenglifeng1@huawei.com, sumitg@nvidia.com,
zhanjie9@hisilicon.com, geert+renesas@glider.be,
cuiyunhui@bytedance.com, vanshikonda@os.amperecomputing.com,
ionela.voinescu@arm.com, jeremy.linton@arm.com,
viresh.kumar@linaro.org, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org,
acpica-devel@lists.linux.dev, linuxarm@huawei.com,
Pengjie Zhang <zhangpengjie2@huawei.com>
Cc: kernel-team@android.com, Will Deacon <will@kernel.org>,
prime.zeng@hisilicon.com, wanghuiqiang@huawei.com,
xuwei5@huawei.com, lihuisong@huawei.com, yubowen8@huawei.com,
wangzhi12@huawei.com
Subject: Re: [PATCH v2 0/2] CPPC: reduce FFH feedback-counter sampling skew on arm64
Date: Wed, 22 Jul 2026 22:39:35 +0100 [thread overview]
Message-ID: <178475048433.1329854.7282103675861242164.b4-ty@kernel.org> (raw)
In-Reply-To: <20260708082818.808041-1-zhangpengjie2@huawei.com>
On Wed, 08 Jul 2026 16:28:16 +0800, Pengjie Zhang wrote:
> The legacy CPPC feedback-counter path reads the delivered and reference
> performance counters separately.
>
> On arm64 systems using AMU-backed CPPC FFH counters, each FFH read is
> served through a cross-CPU counter read helper. Reading the counters
> separately therefore widens the sampling window between them and can
> skew the delivered/reference ratio used by cpuinfo_cur_freq. Under heavy
> load, the skew is observable as transient values that may exceed the
> platform maximum, as discussed in [1] and [2].
>
> [...]
Applied to arm64 (for-next/acpi), thanks!
[1/2] ACPI: CPPC: add paired FFH feedback-counter read hook
https://git.kernel.org/arm64/c/9aa7df520523
[2/2] arm64: topology: read CPPC FFH feedback counters in one operation
https://git.kernel.org/arm64/c/42971d5329d9
Cheers,
--
Will
https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev
prev parent reply other threads:[~2026-07-22 21:40 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-08 8:28 Pengjie Zhang
2026-07-08 8:28 ` [PATCH v2 1/2] ACPI: CPPC: add paired FFH feedback-counter read hook Pengjie Zhang
2026-07-21 12:17 ` Rafael J. Wysocki (Intel)
2026-07-08 8:28 ` [PATCH v2 2/2] arm64: topology: read CPPC FFH feedback counters in one operation Pengjie Zhang
2026-07-09 6:11 ` Jeremy Linton
2026-07-10 13:35 ` Beata Michalska
2026-07-09 6:07 ` [PATCH v2 0/2] CPPC: reduce FFH feedback-counter sampling skew on arm64 Jeremy Linton
2026-07-10 13:42 ` Beata Michalska
2026-07-17 1:24 ` Pengjie Zhang
2026-07-22 21:39 ` Will Deacon [this message]
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