From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753590Ab3AGDim (ORCPT ); Sun, 6 Jan 2013 22:38:42 -0500 Received: from mail-pb0-f46.google.com ([209.85.160.46]:48216 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753395Ab3AGDik (ORCPT ); Sun, 6 Jan 2013 22:38:40 -0500 Date: Sun, 6 Jan 2013 19:38:35 -0800 (PST) From: Hugh Dickins X-X-Sender: hugh@eggly.anvils To: Dave Jones cc: Linus Torvalds , Andrea Arcangeli , Andrew Morton , linux-kernel@vger.kernel.org Subject: Re: oops in copy_page_rep() In-Reply-To: <20130107003718.GA1336@redhat.com> Message-ID: References: <20130105152208.GA3386@redhat.com> <20130107003718.GA1336@redhat.com> User-Agent: Alpine 2.00 (LNX 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 6 Jan 2013, Dave Jones wrote: > > investigating the huge page theory a little further I'm a bit confused. > The kernel on that machine has THP enabled, and the cpu supports it (an old amd64), but.. > > $ cat /sys/kernel/mm/hugepages/hugepages-2048kB/* > 0 > 0 > 0 > 0 > 0 > 0 > > I was expecting at least one of those to be non-zero. > > /sys/kernel/mm/transparent_hugepage/khugepaged/full_scans and pages_collapsed > are both non-zero, so it's been busy doing _something_. > > Is this expected behaviour ? Yes. /sys/kernel/mm/hugepages/ is all about those dusty old opaque hugepages you might have got from fs/hugetlbfs and mm/hugetlb.c; whereas the splitting issue we suspect is peculiar to the dazzling new transparent hugepages you get from mm/huge_memory.c. Hugh