[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] backport request for Xen 4.2 and 4.1 of cs 26287:127c2c47d440


  • To: xen-devel <xen-devel@xxxxxxxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxx>
  • From: Juergen Gross <juergen.gross@xxxxxxxxxxxxxx>
  • Date: Fri, 08 Feb 2013 09:20:13 +0100
  • Delivery-date: Fri, 08 Feb 2013 08:20:30 +0000
  • Domainkey-signature: s=s1536a; d=ts.fujitsu.com; c=nofws; q=dns; h=X-SBRSScore:X-IronPort-AV:Received:X-IronPort-AV: Received:Received:Message-ID:Date:From:Organization: User-Agent:MIME-Version:To:Subject:References:In-Reply-To: Content-Type:Content-Transfer-Encoding; b=QiWL4a5kBNyCFlPMVemEBiIkBTWL6T5hqjyv7HtGJ4OjWq/Cd/S0s8su JmXteXgoY6VgsTx7apPagAYjCAIN+TvQg7s9E2XvoK0tZ5ZmyCcvDGwNO hglWppxxSDqUzBusTPBRlxNd23cAjejltBHPi0HpAHDy97zlr+ycyzTuL sqtYa2xFaR8pM9EHYW01why8JyQ83bAeLcicfpvBy96opqSblNgxpKvkv yWChz25++0gr26PZ3uGlod08uMD+Y;
  • List-id: Xen developer discussion <xen-devel.lists.xen.org>

Ping?

Am 25.01.2013 10:49, schrieb Juergen Gross:
Hi,

I request backport of changeset 26287:127c2c47d440 to Xen 4.2 and Xen 4.1.

Without this change we experience Dom0 lockups when cpupool0 has all
cpus but
one on a single socket and xen ticketlocks are disabled in Dom0.

Some background information:

Disabling ticketlocks in Dom0 was done to avoid lock starvation on certain
workloads with one lock in Dom0 taken at a higher frequency as ticketlock
processing would allow (the poll hypercall was much more expensive than
waiting
for the lock via spinning). In our configuration Dom0 is the only domain in
cpupool0 so using xen ticketlocks shouldn't be an advantage.

The Dom0 lockup happened when one vcpu was holding the xtime_lock while all
other vcpus tried to grab it and none of the vcpus was running on the
single
core on the other socket. At some time all vcpus were spinning and the one
core was idle without being considered for vcpu migration (this should be
addressed by the changeset above). As none of the vcpus would give up
control
voluntarily the complete time slice is used with one vcpu of Dom0 having no
physical processor to run on. During that time the next timer interrupt
will
be pending leading to another request of the xtime_lock which will
trigger the
same loop over and over again.


Juergen



--
Juergen Gross                 Principal Developer Operating Systems
PBG PDG ES&S SWE OS6                   Telephone: +49 (0) 89 3222 2967
Fujitsu Technology Solutions              e-mail: juergen.gross@xxxxxxxxxxxxxx
Domagkstr. 28                           Internet: ts.fujitsu.com
D-80807 Muenchen                 Company details: ts.fujitsu.com/imprint.html

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel


 


Rackspace

Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.