mirror of https://lore.kernel.org/lkml/
 help / color / mirror / Atom feed
From: Dan Magenheimer <dan.magenheimer@oracle.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Subject: tsc reliability for Intel Core 2 Duo "Conroe"
Date: Wed, 26 May 2010 10:41:43 -0700 (PDT)	[thread overview]
Message-ID: <d1278473-1065-4607-98e0-67f2b985ec15@default> (raw)

Looking through code following up on the separate TSC-related
thread, I noticed that my Intel Core 2 Duo "Conroe" box
is determined to have an unstable TSC, so falls back
to clocksource==hpet.

While a Conroe has X86_FEATURE_CONSTANT_TSC and not
X86_FEATURE_NONSTOP_TSC, a Conroe is only able to enter
C0 and C1 (unlike its sister Intel Core 2 Duo processor
"Merom" which can enter C0-C3).

I was under the impression (possibly from an earlier kernel
version?) that tsc_constant PLUS inability to enter deep-C
states would result in an acceptably stable TSC to use
as a clocksource (assuming it passes a TSC warp test).

So is this a bug?  Or is my impression incorrect?

See tsc_check_state() in drivers/acpi/processor_idle.c.
I can submit a patch, but wanted to check first.

             reply	other threads:[~2010-05-26 17:42 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-05-26 17:41 Dan Magenheimer [this message]
2010-05-26 22:21 ` Venkatesh Pallipadi
2010-05-26 23:26   ` Dan Magenheimer
2010-05-27 16:26     ` Dan Magenheimer

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=d1278473-1065-4607-98e0-67f2b985ec15@default \
    --to=dan.magenheimer@oracle.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=tglx@linutronix.de \
    /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
all inboxes | Powered by JetHome®