From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [PATCH] kvm: irqchip: Break up high order allocations of kvm_irq_routing_table Date: Mon, 11 May 2015 13:45:15 +0200 Message-ID: <5550964B.6020001@redhat.com> References: <1431088304-11365-1-git-send-email-joro@8bytes.org> <554CE3A5.7000101@redhat.com> <20150511112522.GJ5438@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Cc: Joerg Roedel , Gleb Natapov , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Christian Borntraeger To: Joerg Roedel Return-path: Received: from mx1.redhat.com ([209.132.183.28]:37751 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753488AbbEKLph (ORCPT ); Mon, 11 May 2015 07:45:37 -0400 In-Reply-To: <20150511112522.GJ5438@suse.de> Sender: kvm-owner@vger.kernel.org List-ID: On 11/05/2015 13:25, Joerg Roedel wrote: >> > It probably doesn't matter much indeed, but can you time the difference? >> > kvm_set_irq_routing is not too frequent, but happens enough often that >> > we had to use a separate SRCU instance just to speed it up (see commit >> > 719d93cd5f5, kvm/irqchip: Speed up KVM_SET_GSI_ROUTING, 2014-01-16). > The results vary a lot, but what I can say for sure is that the > kvm_set_irq_routing function takes at least twice as long (~10.000 vs > ~22.000 cycles) as before on my AMD Kaveri machine (maximum was between > 3-4 times as long). > > On the other side this function is only called 2 times at boot in my > test, so I couldn't detect a noticable effect on the overall boot time > of the guest (37 disks were attached). Christian, can you test this? Paolo