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, 25 Sep 2015 09:50:37 +0200 Message-ID: <5604FCCD.2090100@redhat.com> References: <1442572493-51400-1-git-send-email-dahi@linux.vnet.ibm.com> <55FBED5E.4060600@de.ibm.com> <55FBF5B2.6090907@redhat.com> <5603D928.7000606@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 mail-wi0-f180.google.com ([209.85.212.180]:33108 "EHLO mail-wi0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752908AbbIYHuo (ORCPT ); Fri, 25 Sep 2015 03:50:44 -0400 Received: by wiclk2 with SMTP id lk2so10559203wic.0 for ; Fri, 25 Sep 2015 00:50:43 -0700 (PDT) In-Reply-To: <5603D928.7000606@de.ibm.com> Sender: kvm-owner@vger.kernel.org List-ID: On 24/09/2015 13:06, Christian Borntraeger wrote: > Am 18.09.2015 um 13:29 schrieb Paolo Bonzini: >> >> >> 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? > > Any guidance from your side? All different proposals are certainly ok. > Are you going to take Davids patch or shall he respin? I've committed the patch as is, and I'm preparing a pull request. Paolo