From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qc0-f170.google.com (mail-qc0-f170.google.com [209.85.216.170]) by kanga.kvack.org (Postfix) with ESMTP id 14CB96B0038 for ; Tue, 18 Feb 2014 17:13:05 -0500 (EST) Received: by mail-qc0-f170.google.com with SMTP id e9so26704960qcy.15 for ; Tue, 18 Feb 2014 14:13:04 -0800 (PST) Received: from shelob.surriel.com (shelob.surriel.com. [2002:4a5c:3b41:1:216:3eff:fe57:7f4]) by mx.google.com with ESMTPS id h3si11300144qah.174.2014.02.18.14.12.57 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Tue, 18 Feb 2014 14:13:03 -0800 (PST) From: riel@redhat.com Subject: [PATCH -mm 0/3] fix numa vs kvm scalability issue Date: Tue, 18 Feb 2014 17:12:43 -0500 Message-Id: <1392761566-24834-1-git-send-email-riel@redhat.com> Sender: owner-linux-mm@kvack.org List-ID: To: linux-kernel@vger.kernel.org Cc: kvm@vger.kernel.org, linux-mm@kvack.org, peterz@infradead.org, chegu_vinod@hp.com, aarcange@redhat.com, akpm@linux-foundation.org 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. -- 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