From: Scott Wood <scottwood@freescale.com>
To: Torsten Duwe <duwe@lst.de>
Cc: Tom Musta <tommusta@gmail.com>,
Peter Zijlstra <peterz@infradead.org>,
Raghavendra KT <raghavendra.kt.linux@gmail.com>,
Raghavendra KT <raghavendra.kt@linux.vnet.ibm.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Paul Mackerras <paulus@samba.org>,
Anton Blanchard <anton@samba.org>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
linuxppc-dev@lists.ozlabs.org, Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH v2] powerpc ticket locks
Date: Tue, 11 Feb 2014 12:30:55 -0600 [thread overview]
Message-ID: <1392143455.6733.386.camel@snotra.buserror.net> (raw)
In-Reply-To: <20140211104030.GG2107@lst.de>
On Tue, 2014-02-11 at 11:40 +0100, Torsten Duwe wrote:
> On Tue, Feb 11, 2014 at 03:23:51PM +0530, Raghavendra KT wrote:
> > How much important to have holder information for PPC? From my
> > previous experiment
> > on x86, it was lock-waiter preemption which is problematic rather than
> > lock-holder preemption.
>
> It's something very special to IBM pSeries: the hypervisor can assign
> fractions of physical CPUs to guests. Sometimes a guest with 4 quarter
> CPUs will be faster than 1 monoprocessor. (correct me if I'm wrong).
>
> The directed yield resolves the silly situation when holder and waiter
> reside on the same physical CPU, as I understand it.
>
> x86 has nothing comparable.
How is this different from the very ordinary case of an SMP KVM guest
whose vcpus are not bound to host cpus, and thus you could have multiple
vcpus running on the same host cpu?
-Scott
next prev parent reply other threads:[~2014-02-11 18:31 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-07 16:58 [PATCH v2] powerpc ticket locks Torsten Duwe
2014-02-07 17:12 ` Peter Zijlstra
2014-02-07 17:55 ` Torsten Duwe
2014-02-10 3:10 ` Benjamin Herrenschmidt
2014-02-10 15:52 ` Torsten Duwe
2014-02-10 17:53 ` Peter Zijlstra
2014-02-11 2:44 ` Benjamin Herrenschmidt
2014-02-11 2:56 ` Al Viro
2014-02-11 3:38 ` Benjamin Herrenschmidt
2014-02-11 9:53 ` Raghavendra KT
2014-02-11 10:40 ` Torsten Duwe
2014-02-11 18:30 ` Scott Wood [this message]
2014-02-11 19:34 ` Benjamin Herrenschmidt
2014-02-11 9:39 ` Raghavendra KT
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=1392143455.6733.386.camel@snotra.buserror.net \
--to=scottwood@freescale.com \
--cc=anton@samba.org \
--cc=duwe@lst.de \
--cc=linux-kernel@vger.kernel.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=mingo@kernel.org \
--cc=paulmck@linux.vnet.ibm.com \
--cc=paulus@samba.org \
--cc=peterz@infradead.org \
--cc=raghavendra.kt.linux@gmail.com \
--cc=raghavendra.kt@linux.vnet.ibm.com \
--cc=tommusta@gmail.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).