Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966732Ab3E2OCY (ORCPT ); Wed, 29 May 2013 10:02:24 -0400 Received: from e23smtp05.au.ibm.com ([202.81.31.147]:38386 "EHLO e23smtp05.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S966696Ab3E2OCU (ORCPT ); Wed, 29 May 2013 10:02:20 -0400 Message-ID: <51A60A64.2080509@linux.vnet.ibm.com> Date: Wed, 29 May 2013 22:02:12 +0800 From: Xiao Guangrong User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130110 Thunderbird/17.0.2 MIME-Version: 1.0 To: Marcelo Tosatti CC: gleb@redhat.com, avi.kivity@gmail.com, pbonzini@redhat.com, linux-kernel@vger.kernel.org, kvm@vger.kernel.org Subject: Re: [PATCH v7 04/11] KVM: MMU: zap pages in batch References: <1369252560-11611-1-git-send-email-xiaoguangrong@linux.vnet.ibm.com> <1369252560-11611-5-git-send-email-xiaoguangrong@linux.vnet.ibm.com> <20130524203432.GB4525@amt.cnet> <51A2C2DC.6080403@linux.vnet.ibm.com> <20130528001802.GB1359@amt.cnet> <51A4C6F1.9000607@linux.vnet.ibm.com> <20130529111132.GA5931@amt.cnet> <51A5FDF5.8020003@linux.vnet.ibm.com> <20130529133243.GG5931@amt.cnet> In-Reply-To: <20130529133243.GG5931@amt.cnet> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13052913-1396-0000-0000-00000309FC30 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2134 Lines: 63 On 05/29/2013 09:32 PM, Marcelo Tosatti wrote: > On Wed, May 29, 2013 at 09:09:09PM +0800, Xiao Guangrong wrote: >> This information is I replied Gleb in his mail where he raced a question that >> why "collapse tlb flush is needed": >> >> ====== >> It seems no. >> Since we have reloaded mmu before zapping the obsolete pages, the mmu-lock >> is easily contended. I did the simple track: >> >> + int num = 0; >> restart: >> list_for_each_entry_safe_reverse(sp, node, >> &kvm->arch.active_mmu_pages, link) { >> @@ -4265,6 +4265,7 @@ restart: >> if (batch >= BATCH_ZAP_PAGES && >> cond_resched_lock(&kvm->mmu_lock)) { >> batch = 0; >> + num++; >> goto restart; >> } >> >> @@ -4277,6 +4278,7 @@ restart: >> * may use the pages. >> */ >> kvm_mmu_commit_zap_page(kvm, &invalid_list); >> + printk("lock-break: %d.\n", num); >> } >> >> I do read pci rom when doing kernel building in the guest which >> has 1G memory and 4vcpus with ept enabled, this is the normal >> workload and normal configuration. >> >> # dmesg >> [ 2338.759099] lock-break: 8. >> [ 2339.732442] lock-break: 5. >> [ 2340.904446] lock-break: 3. >> [ 2342.513514] lock-break: 3. >> [ 2343.452229] lock-break: 3. >> [ 2344.981599] lock-break: 4. >> >> Basically, we need to break many times. > > Should measure kvm_mmu_zap_all latency. > >> ====== >> >> You can see we should break 3 times to zap all pages even if we have zapoed >> 10 pages in batch. It is obviously that it need break more times without >> batch-zapping. > > Again, breaking should be no problem, what matters is latency. Please > measure kvm_mmu_zap_all latency after all optimizations to justify > this minimum batching. Okay, okay. I will benchmark the latency. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/