linux-kernel - Re: [PATCH] PM QoS: Add debugfs support to view the list of constraints

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <7h1to0h7a0.fsf@deeprootsystems.com>
Date:	Mon, 15 Dec 2014 14:34:15 -0800
From:	Kevin Hilman <khilman@...nel.org>
To:	Dave Gerlach <d-gerlach@...com>
Cc:	<linux-kernel@...r.kernel.org>, <linux-pm@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Pavel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>,
	Nishanth Menon <nm@...com>
Subject: Re: [PATCH] PM QoS: Add debugfs support to view the list of constraints

Dave Gerlach <d-gerlach@...com> writes:

> From: Nishanth Menon <nm@...com>
>
> PM QoS requests are notoriously hard to debug and made even
> more so due to their highly dynamic nature. Having visibility
> into the internal data representation per constraint allows
> us to have much better appreciation of potential issues or
> bad usage by drivers in the system.
>
> So introduce for all classes of PM QoS, an entry in
> /sys/kernel/debug/pm_qos that shall show all the current
> requests as well as the snapshot of the value these requests
> boil down to. For example:
> ==> /sys/kernel/debug/pm_qos/cpu_dma_latency <==
> 1: 4444: Active
> 2: 2000000000: Default
> 3: 2000000000: Default
> 4: 2000000000: Default
> Type=Minimum, Value=4444, Requests: active=1 / total=4
>
> ==> /sys/kernel/debug/pm_qos/memory_bandwidth <==
> Empty!
>
> ...
>
> The actual value listed will have their meaning based
> on the QoS it is on, the 'Type' indicates what logic
> it would use to collate the information - Minimum,
> Maximum, or Sum. Value is the collation of all requests.
> This interface also compares the values with the defaults
> for the QoS class and marks the ones that are
> currently active.
>
> Signed-off-by: Nishanth Menon <nm@...com>
> Signed-off-by: Dave Gerlach <d-gerlach@...com>

A very useful feature indeed,

Acked-by: Kevin Hilman <khilman@...aro.org>

Kevin
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/