From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [PATCH] KVM: disable halt_poll_ns as default for s390x Date: Fri, 18 Sep 2015 13:29:54 +0200 Message-ID: <55FBF5B2.6090907@redhat.com> References: <1442572493-51400-1-git-send-email-dahi@linux.vnet.ibm.com> <55FBED5E.4060600@de.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Transfer-Encoding: 7bit Cc: wanpeng.li@hotmail.com, dmatlack@google.com, rkrcmar@redhat.com To: Christian Borntraeger , David Hildenbrand , kvm@vger.kernel.org Return-path: Received: from mx1.redhat.com ([209.132.183.28]:42256 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752808AbbIRL37 (ORCPT ); Fri, 18 Sep 2015 07:29:59 -0400 In-Reply-To: <55FBED5E.4060600@de.ibm.com> Sender: kvm-owner@vger.kernel.org List-ID: On 18/09/2015 12:54, Christian Borntraeger wrote: > > -/* halt polling only reduces halt latency by 5-7 us, 500us is enough */ > > -static unsigned int halt_poll_ns = 500000; > > +/* Architectures should define their poll value according to the halt latency */ > > +static unsigned int halt_poll_ns = KVM_HALT_POLL_NS_DEFAULT; > > Yes, I prefer this over disabling it via Kconfig. There are benchmarks which > benefit from polling on s390. Furthermore it seems that the latency > strongly depends on timing of the architecture so making it per arch is > probably the right thing to do. Perhaps a #ifndef is better than replicating the 500us default in all architectures? Or should the default be 0? Paolo