From: David Laight <David.Laight@ACULAB.COM>
To: "'artem.bityutskiy@linux.intel.com'"
<artem.bityutskiy@linux.intel.com>,
"'Rafael J. Wysocki'" <rjw@rjwysocki.net>,
Linux PM <linux-pm@vger.kernel.org>
Cc: Linux ACPI <linux-acpi@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Len Brown <len.brown@intel.com>, Zhang Rui <rui.zhang@intel.com>,
David Box <david.e.box@linux.intel.com>,
"Rafael J. Wysocki" <rafael@kernel.org>
Subject: RE: [PATCH 2/2] intel_idle: Introduce 'states_off' module parameter
Date: Fri, 31 Jan 2020 11:54:13 +0000 [thread overview]
Message-ID: <6cf71f6964c6433abeaf445847c97611@AcuMS.aculab.com> (raw)
In-Reply-To: <28a92577c83276baf355dc8de272a79dc854025a.camel@linux.intel.com>
From: Artem Bityutskiy >
> Sent: 31 January 2020 11:24
> On Fri, 2020-01-31 at 11:07 +0000, David Laight wrote:
> > Unless you know exactly which cpu table is being used the
> > only constraint a user can request is the latency.
>
> Hi David,
>
> in all my use-cases I always know what is the CPU I am dealing with and
> what are the C-states. Simply because in my view they are always CPU-
> dependent in terms of what they do and how are they named.
>
> What you say sounds to me like you would want to disable some C-states
> without knowing anything (or much) about the CPU you are dealing with
> and the C-state names.
>
> If so, could you please share examples of such use-cases?
Dunno, but clearly you want to disable (say) C3 while leaving C6
enabled.
I was trying to find why it was taking 600+us for a RT process
to get rescheduled when it had only been sleeping for a few us.
I found where it was sleeping, but that didn't help at all.
Someone pointed me at a 'random' pdf that referred to /dev/cpu_dma_latency.
Setting that to a small value (eg 20) helps no end.
But there are no references in the code or man pages to that.
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2020-01-31 11:54 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-30 14:44 [PATCH 0/2] intel_idle: Two new module parameters Rafael J. Wysocki
2020-01-30 14:46 ` [PATCH 1/2] intel_idle: Introduce 'use_acpi' module parameter Rafael J. Wysocki
2020-02-02 14:23 ` kbuild test robot
2020-01-30 14:47 ` [PATCH 2/2] intel_idle: Introduce 'states_off' " Rafael J. Wysocki
2020-01-31 11:07 ` David Laight
2020-01-31 11:23 ` Rafael J. Wysocki
2020-01-31 11:24 ` Artem Bityutskiy
2020-01-31 11:54 ` David Laight [this message]
2020-01-31 12:03 ` Rafael J. Wysocki
2020-02-03 11:13 ` [PATCH v2 0/2] intel_idle: Two new module parameters Rafael J. Wysocki
2020-02-03 11:15 ` [PATCH v2 1/2] intel_idle: Introduce 'use_acpi' module parameter Rafael J. Wysocki
2020-02-03 11:19 ` [PATCH v2 2/2] intel_idle: Introduce 'states_off' " Rafael J. Wysocki
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=6cf71f6964c6433abeaf445847c97611@AcuMS.aculab.com \
--to=david.laight@aculab.com \
--cc=artem.bityutskiy@linux.intel.com \
--cc=david.e.box@linux.intel.com \
--cc=len.brown@intel.com \
--cc=linux-acpi@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-pm@vger.kernel.org \
--cc=rafael@kernel.org \
--cc=rjw@rjwysocki.net \
--cc=rui.zhang@intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).