From: Arjan van de Ven <arjan@infradead.org>
To: Luming Yu <luming.yu@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>, LKML <linux-kernel@vger.kernel.org>,
suresh.b.siddha@intel.com, venkatesh.pallipadi@intel.com,
Thomas Gleixner <tglx@linutronix.de>,
"H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [RFC patch] Use IPI_shortcut for lapic timer broadcast
Date: Mon, 29 Jun 2009 07:01:23 -0700 [thread overview]
Message-ID: <20090629070123.5e874497@infradead.org> (raw)
In-Reply-To: <3877989d0906290143y3b5306f4s4a990ecbfbfc49b6@mail.gmail.com>
On Mon, 29 Jun 2009 16:43:16 +0800
Luming Yu <luming.yu@gmail.com> wrote:
> > Even a Pentium-5 100 MHz dual box was able to do cross-CPU IPIs
> > within 10-20 microseconds more than a decade ago - so 50-100 usecs
> > latency on a modern platform is totally out of this planet and will
> > hurt Linux performance big time. And the worst thing about it is
> > that none of the usual performance metrics will really show _why_
> > performance is tanking ...
> >
>
>
> Please note this is deep-C-state related.
> C state does add extra latency.. but I don't know how much...
C states normally only add on the "wait for" side, not on the "send"
side.
(RHEL5 is rather old, so it may have done things a bit different)
Maybe it is time for mainline to not allow a !NO_HZ config....
--
Arjan van de Ven Intel Open Source Technology Centre
For development, discussion and tips for power savings,
visit http://www.lesswatts.org
next prev parent reply other threads:[~2009-06-29 14:00 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-06-29 6:47 [RFC patch] Use IPI_shortcut for lapic timer broadcast Luming Yu
2009-06-29 7:20 ` Ingo Molnar
2009-06-29 8:04 ` Luming Yu
2009-06-29 8:16 ` Ingo Molnar
2009-06-29 8:21 ` Luming Yu
2009-06-29 8:30 ` Ingo Molnar
2009-06-29 8:43 ` Luming Yu
2009-06-29 9:15 ` Ingo Molnar
2009-06-29 14:01 ` Arjan van de Ven [this message]
2009-06-29 20:34 ` Pallipadi, Venkatesh
2009-06-30 7:01 ` Luming Yu
2009-07-03 0:23 ` Pallipadi, Venkatesh
2009-07-03 2:04 ` Luming Yu
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=20090629070123.5e874497@infradead.org \
--to=arjan@infradead.org \
--cc=hpa@zytor.com \
--cc=linux-kernel@vger.kernel.org \
--cc=luming.yu@gmail.com \
--cc=mingo@elte.hu \
--cc=suresh.b.siddha@intel.com \
--cc=tglx@linutronix.de \
--cc=venkatesh.pallipadi@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