From nobody Mon Feb 9 07:55:07 2026 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.com: domain of redhat.com designates 209.132.183.28 as permitted sender) client-ip=209.132.183.28; envelope-from=libvir-list-bounces@redhat.com; helo=mx1.redhat.com; Authentication-Results: mx.zohomail.com; spf=pass (zoho.com: domain of redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=libvir-list-bounces@redhat.com; dmarc=pass(p=none dis=none) header.from=redhat.com ARC-Seal: i=1; a=rsa-sha256; t=1559205203; cv=none; d=zoho.com; s=zohoarc; b=DOhMc8KpA4s2hQMF0zrmaFIIbjcfar5lXXU68ManxkEbxYijocadW5MQv8bbYQAQs5knbSE0q3tD4ApLnETSYOTZHoLzQnZH76xoA2XgeFlmpJdgOHHBjEsoiHtS+g/JFKwgZctBqpYtWbHo6AIlqOvxPYXGIYmUeclDqpKNPYM= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zoho.com; s=zohoarc; t=1559205203; h=Content-Type:Content-Transfer-Encoding:Cc:Date:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:To:ARC-Authentication-Results; bh=EIvg2H1mlrMHsFXnwjtYrhQ4U2p0SeTUU++ouEnaH9c=; b=EervOho09AQT4hnAo7X8F6bWHPiqs353t29UNBgdiYht02UyeTFyuh7MehD4GqT6EEPjgkydaarHv0a8pnTOVlr9zZ8C044XoY6xM1syOOefPtN8blqvZpGwCZmmUlQ5e6KFXzvTmMh9hUudEBknJmaRzulR5hR77EPNdIWUO+I= ARC-Authentication-Results: i=1; mx.zoho.com; spf=pass (zoho.com: domain of redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=libvir-list-bounces@redhat.com; dmarc=pass header.from= (p=none dis=none) header.from= Return-Path: Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by mx.zohomail.com with SMTPS id 1559205203234634.0051348610167; Thu, 30 May 2019 01:33:23 -0700 (PDT) Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id A7D17C0AD2AC; Thu, 30 May 2019 08:33:10 +0000 (UTC) Received: from colo-mx.corp.redhat.com (colo-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.20]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 53E2E1009976; Thu, 30 May 2019 08:33:02 +0000 (UTC) Received: from lists01.pubmisc.prod.ext.phx2.redhat.com (lists01.pubmisc.prod.ext.phx2.redhat.com [10.5.19.33]) by colo-mx.corp.redhat.com (Postfix) with ESMTP id 8785C1806B11; Thu, 30 May 2019 08:32:52 +0000 (UTC) Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) by lists01.pubmisc.prod.ext.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id x4U8WoOr015838 for ; Thu, 30 May 2019 04:32:50 -0400 Received: by smtp.corp.redhat.com (Postfix) id 052371009976; Thu, 30 May 2019 08:32:50 +0000 (UTC) Received: from dell-r430-03.lab.eng.brq.redhat.com (dell-r430-03.lab.eng.brq.redhat.com [10.37.153.18]) by smtp.corp.redhat.com (Postfix) with ESMTP id B5D991001E86; Thu, 30 May 2019 08:32:47 +0000 (UTC) From: Igor Mammedov To: qemu-devel@nongnu.org Date: Thu, 30 May 2019 10:33:18 +0200 Message-Id: <1559205199-233510-3-git-send-email-imammedo@redhat.com> In-Reply-To: <1559205199-233510-1-git-send-email-imammedo@redhat.com> References: <1559205199-233510-1-git-send-email-imammedo@redhat.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-loop: libvir-list@redhat.com Cc: libvir-list@redhat.com, pbonzini@redhat.com, ehabkost@redhat.com Subject: [libvirt] [PATCH v4 2/3] numa: deprecate 'mem' parameter of '-numa node' option X-BeenThere: libvir-list@redhat.com X-Mailman-Version: 2.1.12 Precedence: junk List-Id: Development discussions about the libvirt library & tools List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Sender: libvir-list-bounces@redhat.com Errors-To: libvir-list-bounces@redhat.com X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Thu, 30 May 2019 08:33:21 +0000 (UTC) Content-Type: text/plain; charset="utf-8" The parameter allows to configure fake NUMA topology where guest VM simulates NUMA topology but not actually getting performance benefits from it. The same or better results could be achieved using 'memdev' parameter. Beside of unpredictable performance, '-numa node.mem' option has other issues when it's used with combination of -mem-path + + -mem-prealloc + memdev backends (pc-dimm), breaking binding of memdev backends since mem-path/mem-prealloc are global and affect the most of RAM allocations. It's possible to make memdevs and global -mem-path/mem-prealloc to play nicely together but that will just complicate already complicated code and add unobious ways it could break on 2 different memmory allocation pathes and their combinations. Instead of it, consolidate all guest RAM allocation over memdev which still allows to create fake NUMA configurations if desired and leaves one simplifyed code path to consider when it comes to guest RAM allocation. To achieve desired simplification deprecate 'mem' parameter as its ad-hoc partitioning of initial RAM MemoryRegion can't be translated to memdev based backend transparently to users and in compatible manner (migration wise). Later down the road that will allow to consolidate means of how guest RAM is allocated and would permit us to clean up quite a bit memory allocations and numa code, leaving only 'memdev' implementation in place. Signed-off-by: Igor Mammedov --- Notes: v4: * fix up documentation to mention where users should look to check if -numa node.mem is supported numa.c | 2 ++ qemu-deprecated.texi | 16 ++++++++++++++++ 2 files changed, 18 insertions(+) diff --git a/numa.c b/numa.c index 3875e1e..2205773 100644 --- a/numa.c +++ b/numa.c @@ -121,6 +121,8 @@ static void parse_numa_node(MachineState *ms, NumaNodeO= ptions *node, =20 if (node->has_mem) { numa_info[nodenr].node_mem =3D node->mem; + warn_report("Parameter -numa node,mem is deprecated," + " use -numa node,memdev instead"); } if (node->has_memdev) { Object *o; diff --git a/qemu-deprecated.texi b/qemu-deprecated.texi index 50292d8..eb347f5 100644 --- a/qemu-deprecated.texi +++ b/qemu-deprecated.texi @@ -82,6 +82,22 @@ The @code{-realtime mlock=3Don|off} argument has been re= placed by the The ``-virtfs_synth'' argument is now deprecated. Please use ``-fsdev synt= h'' and ``-device virtio-9p-...'' instead. =20 +@subsection -numa node,mem=3D@var{size} (since 4.1) + +The parameter @option{mem} of @option{-numa node} is used to assign a part= of +guest RAM to a NUMA node. But when using it, it's impossible to manage spe= cified +RAM chunk on the host side (like bind it to a host node, setting bind poli= cy, ...), +so guest end-ups with the fake NUMA configuration with suboptiomal perform= ance. +However since 2014 there is an alternative way to assign RAM to a NUMA node +using parameter @option{memdev}, which does the same as @option{mem} and a= dds +means to actualy manage node RAM on the host side. Use parameter @option{m= emdev} +with @var{memory-backend-ram} backend as an replacement for parameter @opt= ion{mem} +to achieve the same fake NUMA effect or a properly configured +@var{memory-backend-file} backend to actually benefit from NUMA configurat= ion. +In future new machine versions will not accept the option but it will still +work with old machine types. User can check QAPI schema to see if the lega= cy +option is supported by looking at MachineInfo::numa-mem-supported property. + @section QEMU Machine Protocol (QMP) commands =20 @subsection block-dirty-bitmap-add "autoload" parameter (since 2.12.0) --=20 2.7.4 -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list