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Wysocki" , Len Brown , Pavel Machek , Greg Kroah-Hartman , Danilo Krummrich , Johan Hovold , linux-pm@vger.kernel.org, driver-core@lists.linux.dev, linux-kernel@vger.kernel.org, Dominik Brodowski Subject: Re: [PATCH 0/3] PM: runtime: add new runtime metrics and summary Message-ID: <20261111101152.00007785@kernel.org> In-Reply-To: References: <20261110-pm-runtime-summary-v1-0-12ebf283db78@kernel.org> X-Mailer: Claws Mail 4.4.0 (GTK 3.24.51; x86_64-w64-mingw32) X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Tue, 10 Nov 2026 19:38:39 -0800 Samuel Wu wrote: ... >=20 > What is the vision for using these runtime PM stats once surfaced to > userspace? Runtime PM and suspend have disjoint portions, but I'm > curious if you see any non-obvious areas where these stats would be > insightful. The main things this is useful for are detecting power "thrashing" and tuning autosuspend delays. Currently, sysfs only shows the total time a device spent in active and suspended mode; from an energy standpoint, a continuous 50 second suspension is different from a device cycling 1000 times for 50ms each (these transitions can be pretty power-hungry). This could help userspace utilities like PowerTOP to more effectively determine what is causing an increased power consumption. =46rom the kernel dev standpoint - this is genuinely useful when testing runtime PM functions in new drivers (for example in the IIO subsystem we deal with a lot of runtime PM stuff). > And is there a reason the stats need to be surfaced in both sysfs and deb= ugfs? sysfs definitely, as you should definitely be able to access this info per-device (and this is the way userspace tools would get this info). The debugfs summary is however pretty elegant IMO and useful. I'm sure a lot of people investigating odd device behaviour would like this (plus there are overviews like this in the kernel already - clk_summary for example). I'll add these points to the cover letter in v2. Thanks. --=20 Kind regards, Joshua Crofts