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=-15.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 7FFF9C433DB for ; Fri, 19 Mar 2021 15:50:53 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id DF37E6195B for ; Fri, 19 Mar 2021 15:50:52 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DF37E6195B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:46588 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lNHOl-0007o2-TF for qemu-devel@archiver.kernel.org; Fri, 19 Mar 2021 11:50:51 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:41560) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lNHNL-00073q-8B for qemu-devel@nongnu.org; Fri, 19 Mar 2021 11:49:23 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:22587) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lNHNJ-0004k8-JM for qemu-devel@nongnu.org; Fri, 19 Mar 2021 11:49:23 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1616168960; 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=5QF6Tn6Ht9GQLRx819QNHuPvUQuEPSWp4pGACwIEdd4=; b=bLzcDhxOm1Ryq9Q09ddoPv551fBqmTCX7KydLDQGN74DpdNFnnokRkiqlXDTCSaymrf0ar l5+B9Dmd2mQX210nqzkqqB0WtBB44cELRSTPnpyWY9wc7Athk+DFKcuQJQAWFfTtDMa3eS KL1uYbxRi35RNQkThRcZd9JUVqKy1AI= 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-20-4ddc1rbHO1elQ7xuEYGE7A-1; Fri, 19 Mar 2021 11:49:18 -0400 X-MC-Unique: 4ddc1rbHO1elQ7xuEYGE7A-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 69827107ACCD; Fri, 19 Mar 2021 15:49:17 +0000 (UTC) Received: from [10.36.112.11] (ovpn-112-11.ams2.redhat.com [10.36.112.11]) by smtp.corp.redhat.com (Postfix) with ESMTP id EDEE15D730; Fri, 19 Mar 2021 15:49:01 +0000 (UTC) To: Markus Armbruster References: <20210319101230.21531-1-david@redhat.com> <20210319101230.21531-14-david@redhat.com> <87ft0ri23r.fsf@dusky.pond.sub.org> From: David Hildenbrand Organization: Red Hat GmbH Subject: Re: [PATCH v4 13/14] qmp: Include "reserve" property of memory backends Message-ID: <84f961a5-6292-8364-9491-f8330b401a65@redhat.com> Date: Fri, 19 Mar 2021 16:49:01 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.0 MIME-Version: 1.0 In-Reply-To: <87ft0ri23r.fsf@dusky.pond.sub.org> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=david@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=david@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.251, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Marcel Apfelbaum , Eduardo Habkost , "Michael S. Tsirkin" , Igor Kotrasinski , Richard Henderson , qemu-devel@nongnu.org, Peter Xu , "Dr. David Alan Gilbert" , Greg Kurz , Paolo Bonzini , Stefan Hajnoczi , Murilo Opsfelder Araujo , Igor Mammedov , =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 19.03.21 16:40, Markus Armbruster wrote: > David Hildenbrand writes: > >> Let's include the new property. >> >> Cc: Eric Blake >> Cc: Markus Armbruster >> Signed-off-by: David Hildenbrand >> --- >> hw/core/machine-qmp-cmds.c | 1 + >> qapi/machine.json | 6 ++++++ >> 2 files changed, 7 insertions(+) >> >> diff --git a/hw/core/machine-qmp-cmds.c b/hw/core/machine-qmp-cmds.c >> index 68a942595a..bd2a7f2dd0 100644 >> --- a/hw/core/machine-qmp-cmds.c >> +++ b/hw/core/machine-qmp-cmds.c >> @@ -174,6 +174,7 @@ static int query_memdev(Object *obj, void *opaque) >> m->merge = object_property_get_bool(obj, "merge", &error_abort); >> m->dump = object_property_get_bool(obj, "dump", &error_abort); >> m->prealloc = object_property_get_bool(obj, "prealloc", &error_abort); >> + m->reserve = object_property_get_bool(obj, "reserve", &error_abort); >> m->policy = object_property_get_enum(obj, "policy", "HostMemPolicy", >> &error_abort); >> host_nodes = object_property_get_qobject(obj, >> diff --git a/qapi/machine.json b/qapi/machine.json >> index c0c52aef10..12860a1f79 100644 >> --- a/qapi/machine.json >> +++ b/qapi/machine.json >> @@ -814,6 +814,11 @@ >> # >> # @prealloc: enables or disables memory preallocation >> # >> +# @reserve: enables or disables reservation of swap space (or huge pages >> +# if applicable). If reservation is enabled (default), actual >> +# reservation depends on underlying OS support. In contrast, >> +# disabling reservation without OS support will bail out. (since 6.1) >> +# > > Provides two settings: "enable reservation if possible", and "disable > reservation or else fail". > > Does "enable reservation or else fail" make no sense, or is it merely > unimplemented? The default for now used to be "enable reservation if possible". For example, Windows always reserves/commits the whole region. Under Linux, reservation is always done for private memory mappings, however, especially for basically all (with one exception) shared memory there is no reservation of any kind (with another exception). For example, it does not make sense to reserve swap space for a file-backed mapping; we can just writeback to the file in case we run out of memory. Therefore, Linux will never reserve swap space in that case. So if we were to implement a "enable reservation or else fail", the default ("true") would no longer work for existing setups. Usually we want "enable reservation if possible" unless in spacial cases ("definitely avoid the reservation") -- Thanks, David / dhildenb