From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751032AbdE3HoR (ORCPT ); Tue, 30 May 2017 03:44:17 -0400 Received: from mx2.suse.de ([195.135.220.15]:46000 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750839AbdE3HoO (ORCPT ); Tue, 30 May 2017 03:44:14 -0400 Date: Tue, 30 May 2017 09:44:08 +0200 From: Michal Hocko To: Mike Rapoport Cc: Vlastimil Babka , "Kirill A. Shutemov" , Andrew Morton , Arnd Bergmann , "Kirill A. Shutemov" , Andrea Arcangeli , Pavel Emelyanov , linux-mm , lkml , Linux API Subject: Re: [PATCH] mm: introduce MADV_CLR_HUGEPAGE Message-ID: <20170530074408.GA7969@dhcp22.suse.cz> References: <20170522114243.2wrdbncilozygbpl@node.shutemov.name> <20170522133559.GE27382@rapoport-lnx> <20170522135548.GA8514@dhcp22.suse.cz> <20170522142927.GG27382@rapoport-lnx> <20170524075043.GB3063@rapoport-lnx> <20170524103947.GC3063@rapoport-lnx> <20170524111800.GD14733@dhcp22.suse.cz> <20170524142735.GF3063@rapoport-lnx> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170524142735.GF3063@rapoport-lnx> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 24-05-17 17:27:36, Mike Rapoport wrote: > On Wed, May 24, 2017 at 01:18:00PM +0200, Michal Hocko wrote: [...] > > Why cannot khugepaged simply skip over all VMAs which have userfault > > regions registered? This would sound like a less error prone approach to > > me. > > khugepaged does skip over VMAs which have userfault. We could register the > regions with userfault before populating them to avoid collapses in the > transition period. Why cannot you register only post-copy regions and "manually" copy the pre-copy parts? > But then we'll have to populate these regions with > UFFDIO_COPY which adds quite an overhead. How big is the performance impact? -- Michal Hocko SUSE Labs From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michal Hocko Subject: Re: [PATCH] mm: introduce MADV_CLR_HUGEPAGE Date: Tue, 30 May 2017 09:44:08 +0200 Message-ID: <20170530074408.GA7969@dhcp22.suse.cz> References: <20170522114243.2wrdbncilozygbpl@node.shutemov.name> <20170522133559.GE27382@rapoport-lnx> <20170522135548.GA8514@dhcp22.suse.cz> <20170522142927.GG27382@rapoport-lnx> <20170524075043.GB3063@rapoport-lnx> <20170524103947.GC3063@rapoport-lnx> <20170524111800.GD14733@dhcp22.suse.cz> <20170524142735.GF3063@rapoport-lnx> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20170524142735.GF3063@rapoport-lnx> Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Mike Rapoport Cc: Vlastimil Babka , "Kirill A. Shutemov" , Andrew Morton , Arnd Bergmann , "Kirill A. Shutemov" , Andrea Arcangeli , Pavel Emelyanov , linux-mm , lkml , Linux API List-Id: linux-api@vger.kernel.org On Wed 24-05-17 17:27:36, Mike Rapoport wrote: > On Wed, May 24, 2017 at 01:18:00PM +0200, Michal Hocko wrote: [...] > > Why cannot khugepaged simply skip over all VMAs which have userfault > > regions registered? This would sound like a less error prone approach to > > me. > > khugepaged does skip over VMAs which have userfault. We could register the > regions with userfault before populating them to avoid collapses in the > transition period. Why cannot you register only post-copy regions and "manually" copy the pre-copy parts? > But then we'll have to populate these regions with > UFFDIO_COPY which adds quite an overhead. How big is the performance impact? -- Michal Hocko SUSE Labs From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f69.google.com (mail-wm0-f69.google.com [74.125.82.69]) by kanga.kvack.org (Postfix) with ESMTP id B77176B0279 for ; Tue, 30 May 2017 03:44:14 -0400 (EDT) Received: by mail-wm0-f69.google.com with SMTP id g143so17931792wme.13 for ; Tue, 30 May 2017 00:44:14 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id k22si12202090edk.210.2017.05.30.00.44.13 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 30 May 2017 00:44:13 -0700 (PDT) Date: Tue, 30 May 2017 09:44:08 +0200 From: Michal Hocko Subject: Re: [PATCH] mm: introduce MADV_CLR_HUGEPAGE Message-ID: <20170530074408.GA7969@dhcp22.suse.cz> References: <20170522114243.2wrdbncilozygbpl@node.shutemov.name> <20170522133559.GE27382@rapoport-lnx> <20170522135548.GA8514@dhcp22.suse.cz> <20170522142927.GG27382@rapoport-lnx> <20170524075043.GB3063@rapoport-lnx> <20170524103947.GC3063@rapoport-lnx> <20170524111800.GD14733@dhcp22.suse.cz> <20170524142735.GF3063@rapoport-lnx> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170524142735.GF3063@rapoport-lnx> Sender: owner-linux-mm@kvack.org List-ID: To: Mike Rapoport Cc: Vlastimil Babka , "Kirill A. Shutemov" , Andrew Morton , Arnd Bergmann , "Kirill A. Shutemov" , Andrea Arcangeli , Pavel Emelyanov , linux-mm , lkml , Linux API On Wed 24-05-17 17:27:36, Mike Rapoport wrote: > On Wed, May 24, 2017 at 01:18:00PM +0200, Michal Hocko wrote: [...] > > Why cannot khugepaged simply skip over all VMAs which have userfault > > regions registered? This would sound like a less error prone approach to > > me. > > khugepaged does skip over VMAs which have userfault. We could register the > regions with userfault before populating them to avoid collapses in the > transition period. Why cannot you register only post-copy regions and "manually" copy the pre-copy parts? > But then we'll have to populate these regions with > UFFDIO_COPY which adds quite an overhead. How big is the performance impact? -- Michal Hocko SUSE Labs -- 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