From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AA247C433DB for ; Thu, 18 Feb 2021 13:06:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5873964E28 for ; Thu, 18 Feb 2021 13:06:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231586AbhBRNFS (ORCPT ); Thu, 18 Feb 2021 08:05:18 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:24953 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230469AbhBRK4c (ORCPT ); Thu, 18 Feb 2021 05:56:32 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1613645705; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=gcqiQcLIQresUmqBjSfx8mrrnANdscT5bovWT1NTSz4=; b=RbMuaZstJ6CrGg4oZoL5YG7svl5DHKGEf1wjaUssrTflC9zkTDIx2aqkNx4R9yEHjj/GQo ivX8Rkt2Fl0Fvr6kT9YAdKWpQ7SnLbk9fTKa3Wrwos/6r4zfOGSVj53QVGRcydY6V8EXbF zZv44dg4pKP5TVkprrvN+0/8wO5f9uk= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-290-9O4f9C2-NQaWM_0J6rqvXQ-1; Thu, 18 Feb 2021 05:55:01 -0500 X-MC-Unique: 9O4f9C2-NQaWM_0J6rqvXQ-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 032E7107ACC7; Thu, 18 Feb 2021 10:54:58 +0000 (UTC) Received: from [10.36.114.59] (ovpn-114-59.ams2.redhat.com [10.36.114.59]) by smtp.corp.redhat.com (Postfix) with ESMTP id 29CF45D9C2; Thu, 18 Feb 2021 10:54:49 +0000 (UTC) Subject: Re: [PATCH RFC] mm/madvise: introduce MADV_POPULATE to prefault/prealloc memory From: David Hildenbrand To: Michal Hocko Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Arnd Bergmann , Oscar Salvador , Matthew Wilcox , Andrea Arcangeli , Minchan Kim , Jann Horn , Jason Gunthorpe , Dave Hansen , Hugh Dickins , Rik van Riel , "Michael S . Tsirkin" , "Kirill A . Shutemov" , Vlastimil Babka , Richard Henderson , Ivan Kokshaysky , Matt Turner , Thomas Bogendoerfer , "James E.J. Bottomley" , Helge Deller , Chris Zankel , Max Filippov , linux-alpha@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linux-xtensa@linux-xtensa.org, linux-arch@vger.kernel.org References: <20210217154844.12392-1-david@redhat.com> <3763a505-02d6-5efe-a9f5-40381acfbdfd@redhat.com> Organization: Red Hat GmbH Message-ID: Date: Thu, 18 Feb 2021 11:54:48 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: <3763a505-02d6-5efe-a9f5-40381acfbdfd@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org >>> If we hit >>> hardware errors on pages, ignore them - nothing we really can or >>> should do. >>> 3. On errors during MADV_POPULATED, some memory might have been >>> populated. Callers have to clean up if they care. >> >> How does caller find out? madvise reports 0 on success so how do you >> find out how much has been populated? > > If there is an error, something might have been populated. In my QEMU > implementation, I simply discard the range again, good enough. I don't > think we need to really indicate "error and populated" or "error and not > populated". Clarifying again: if madvise(MADV_POPULATED) succeeds, it returns 0. If there was a problem poopulating memory, it returns -ENOMEM (similar to MADV_WILLNEED). Callers can detect the error and discard. -- Thanks, David / dhildenb