Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752021AbaATUkx (ORCPT ); Mon, 20 Jan 2014 15:40:53 -0500 Received: from relay3.sgi.com ([192.48.152.1]:34317 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750758AbaATUku (ORCPT ); Mon, 20 Jan 2014 15:40:50 -0500 Date: Mon, 20 Jan 2014 14:41:08 -0600 From: Alex Thorlton To: Oleg Nesterov Cc: "Kirill A. Shutemov" , linux-kernel@vger.kernel.org, Ingo Molnar , Peter Zijlstra , Andrew Morton , "Kirill A. Shutemov" , Benjamin Herrenschmidt , Rik van Riel , Naoya Horiguchi , "Eric W. Biederman" , Andy Lutomirski , Al Viro , Kees Cook , Andrea Arcangeli Subject: Re: [RFC PATCHv2 2/2] Change khugepaged to respect MMF_THP_DISABLE flag Message-ID: <20140120204108.GE18196@sgi.com> References: <1bc8f911363af956b37d8ea415d734f3191f1c78.1389905087.git.athorlton@sgi.com> <13c9d1b0213af7cee7afb54de368a0b189e98df8.1389905087.git.athorlton@sgi.com> <20140118234957.GB10970@node.dhcp.inet.fi> <20140120195812.GD18196@sgi.com> <20140120201525.GA31416@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140120201525.GA31416@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 20, 2014 at 09:15:25PM +0100, Oleg Nesterov wrote: > On 01/20, Alex Thorlton wrote: > > > > No, definitely not. Upon review, khugepaged_test_exit is the wrong > > place to do this check. I think I need to move it up to > > khugepaged_scan_mm_slot for this to work correctly. > > Why? unless a MMF_THP_DISABLE task does madvise(MADV_HUGEPAGE) > khugepaged_scan_mm_slot() should never see its ->mm ? > > Although I got lost a bit, and probably misunderstood... but it > seems to me that whatever you do this patch should not touch > khugepaged_scan_mm_slot. Maybe I've gotten myself confused as well :) After looking through the code some more, my understanding is that khugepaged_test_exit is used to make sure that __khugepaged_exit isn't running from underneath at certain times, so to have khugepaged_test_exit return true when __khugepaged_exit is not necessarily running, seems incorrect to me. I think the check for MMF_THP_DISABLE should occur at the same time as we check khugepaged_test_exit, but should occur separately, since I don't really believe the two checks are related. Something like this in khugepaged_scan_mm_slot: mm = mm_slot->mm; down_read(&mm->mmap_sem); - if (unlikely(khugepaged_test_exit(mm))) + if (unlikely(khugepaged_test_exit(mm) || check_mmf_thp_disable(mm))) vma = NULL; else vma = find_vma(mm, khugepaged_scan.address); progress++; I think this makes more sense, but I may not be looking at this correctly. Thoughts? - Alex -- 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/