From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joerg Roedel Subject: Re: [PATCH] kvm: irqchip: Break up high order allocations of kvm_irq_routing_table Date: Mon, 11 May 2015 13:25:22 +0200 Message-ID: <20150511112522.GJ5438@suse.de> References: <1431088304-11365-1-git-send-email-joro@8bytes.org> <554CE3A5.7000101@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Joerg Roedel , Gleb Natapov , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Christian Borntraeger To: Paolo Bonzini Return-path: Content-Disposition: inline In-Reply-To: <554CE3A5.7000101@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org Hi Paolo, On Fri, May 08, 2015 at 06:26:13PM +0200, Paolo Bonzini 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). Joerg