From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from firstgate.proxmox.com (firstgate.proxmox.com [212.224.123.68]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by lists.proxmox.com (Postfix) with ESMTPS id A2B2362FAB for ; Tue, 14 Jul 2020 18:09:31 +0200 (CEST) Received: from firstgate.proxmox.com (localhost [127.0.0.1]) by firstgate.proxmox.com (Proxmox) with ESMTP id 97EAA287B7 for ; Tue, 14 Jul 2020 18:09:01 +0200 (CEST) Received: from smtp.lightspeed.ca (smtp.lightspeed.ca [206.12.82.4]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by firstgate.proxmox.com (Proxmox) with ESMTPS id 6C64A287A7 for ; Tue, 14 Jul 2020 18:08:59 +0200 (CEST) Received: from static-pppoe.lightspeed.ca ([65.110.28.178] helo=[192.168.0.56]) by smtp.lightspeed.ca with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1jvNRJ-0001aQ-JT for pve-user@lists.proxmox.com; Tue, 14 Jul 2020 09:05:54 -0700 To: pve-user@lists.proxmox.com References: <4900ba10-107e-439c-9716-6e988ae7f5ef@web.de> From: Atila Vasconcelos Message-ID: Date: Tue, 14 Jul 2020 09:05:43 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <4900ba10-107e-439c-9716-6e988ae7f5ef@web.de> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-SPAM-LEVEL: Spam detection results: 0 KAM_DMARC_STATUS 0.01 Test Rule for DKIM or SPF Failure with Strict Alignment NICE_REPLY_A -0.001 Looks like a legit reply (A) SPF_HELO_PASS -0.001 SPF: HELO matches SPF record SPF_PASS -0.001 SPF: sender matches SPF record URIBL_BLOCKED 0.001 ADMINISTRATOR NOTICE: The query to URIBL was blocked. See http://wiki.apache.org/spamassassin/DnsBlocklists#dnsbl-block for more information. [gnu.org, proxmox.com] Subject: Re: [PVE-User] linux idle cpu overhead in kvm - old issue, but still there in 2020... X-BeenThere: pve-user@lists.proxmox.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: Proxmox VE user list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 14 Jul 2020 16:09:31 -0000 Wow, I just tried this at my servers (very old Dell PowerEdge 2950); The results are impressive! 8o ABV On 2020-07-13 3:15 a.m., Roland wrote: > hello, > > i have found that there is an old bug still around in linux, which is > causing quite an amount of unnecessary cpu consumption in kvm/proxmox, > and thus, wasting precious power. > > i run some proxmox installations on older systems and on those, it's > quite significant difference. > > on the slowest system, a single debian 10 VM , kvm process is at 20% cpu > (VM is 100% idle) when this issue is present. > > if i change VMs machine type from i440fx(default) to q35 the problem > goes away. > > the same applies when running "powertop --auto-tune" inside the guest > (with i440fx type - enable autosuspend for usb-controller + tablet > device). > > on some L5630 machine, in proxmox summary i see "CPU usage" drop from > 10% to <1%. > > see: > https://bugzilla.redhat.com/show_bug.cgi?id=478317 > https://bugzilla.redhat.com/show_bug.cgi?id=949547 > > i guess this information could make a difference for people who run a > large amount of virtual machines or use older systems/cpu's. > > on most recent cpu's, i think the difference is not that big. > > anyway, i really wonder how linux bugs have such great survival > capability.... > > regards > roland > > more references: > https://lists.gnu.org/archive/html/qemu-devel/2010-04/msg00149.html > https://www.redhat.com/archives/vfio-users/2015-November/msg00159.html > > > _______________________________________________ > pve-user mailing list > pve-user@lists.proxmox.com > https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-user >