From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ig0-f175.google.com (mail-ig0-f175.google.com [209.85.213.175]) by kanga.kvack.org (Postfix) with ESMTP id A7C016B0031 for ; Wed, 19 Feb 2014 03:59:20 -0500 (EST) Received: by mail-ig0-f175.google.com with SMTP id uq10so9051803igb.2 for ; Wed, 19 Feb 2014 00:59:20 -0800 (PST) Received: from merlin.infradead.org (merlin.infradead.org. [2001:4978:20e::2]) by mx.google.com with ESMTPS id h2si25602950igg.66.2014.02.19.00.59.19 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 19 Feb 2014 00:59:19 -0800 (PST) Date: Wed, 19 Feb 2014 09:59:17 +0100 From: Peter Zijlstra Subject: Re: [PATCH -mm 0/3] fix numa vs kvm scalability issue Message-ID: <20140219085917.GJ27965@twins.programming.kicks-ass.net> References: <1392761566-24834-1-git-send-email-riel@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1392761566-24834-1-git-send-email-riel@redhat.com> Sender: owner-linux-mm@kvack.org List-ID: To: riel@redhat.com Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-mm@kvack.org, chegu_vinod@hp.com, aarcange@redhat.com, akpm@linux-foundation.org On Tue, Feb 18, 2014 at 05:12:43PM -0500, riel@redhat.com wrote: > The NUMA scanning code can end up iterating over many gigabytes > of unpopulated memory, especially in the case of a freshly started > KVM guest with lots of memory. > > This results in the mmu notifier code being called even when > there are no mapped pages in a virtual address range. The amount > of time wasted can be enough to trigger soft lockup warnings > with very large (>2TB) KVM guests. > > This patch moves the mmu notifier call to the pmd level, which > represents 1GB areas of memory on x86-64. Furthermore, the mmu > notifier code is only called from the address in the PMD where > present mappings are first encountered. > > The hugetlbfs code is left alone for now; hugetlb mappings are > not relocatable, and as such are left alone by the NUMA code, > and should never trigger this problem to begin with. > > The series also adds a cond_resched to task_numa_work, to > fix another potential latency issue. Andrew, I'll pick up the first kernel/sched/ patch; do you want the other two mm/ patches? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org