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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 C2182C468BD for ; Fri, 7 Jun 2019 18:22:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AA923208E3 for ; Fri, 7 Jun 2019 18:22:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731387AbfFGSWj (ORCPT ); Fri, 7 Jun 2019 14:22:39 -0400 Received: from mail-wr1-f67.google.com ([209.85.221.67]:34500 "EHLO mail-wr1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730183AbfFGSWj (ORCPT ); Fri, 7 Jun 2019 14:22:39 -0400 Received: by mail-wr1-f67.google.com with SMTP id e16so3102179wrn.1 for ; Fri, 07 Jun 2019 11:22:38 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=eNp/kwCcjJ3WyRs1HdEQeYz66YbQ4zXrLFnd6CGtqfQ=; b=EdgF3WN2ThPxrTFdLDp3bX1Vabyk1PiEmFfRXSIoOUABMnL24ZArXp67cQAmlFvlMa wfPF26Tmrw3yDRcueqKHdzNXAPFd3xfHV2qM5uzHqIUsmg6ACZy93AsQ4DulePKdDwjo B1rAfij0ya+AxWMlYbIDf7BStVmcTPstl63ESEMe+EAi5fTOrkcV3SIHGktnAmfjgNOV 00LxJI6wblplrGzah5s8M89iLSjaSa4l7mjsbhccLpbBzOi4RQh96TjtDevNL417m1F3 MiXBvpZ4rkuwBszF4B/XDR2ibup4CWdr7jRsTytOsPm1WzawLFL2FLqzU/Ts8b8Z1L32 1G3g== X-Gm-Message-State: APjAAAVha9emNF0bRo4GU1q4zl0ik20dhew4ibhyWb9aoYPKJtc26Wj1 Yc4t4d+ipkAqwA6P8ZhvHbVZHw== X-Google-Smtp-Source: APXvYqwrf60J+k2JN6vMRpE7QAF5l8jsltiwzK3HTHX6hWafz/VFEn5A2JWE/ev0sD8j3/Nw/SvQPA== X-Received: by 2002:a5d:414c:: with SMTP id c12mr21816421wrq.88.1559931757855; Fri, 07 Jun 2019 11:22:37 -0700 (PDT) Received: from ?IPv6:2001:b07:6468:f312:d43d:6da3:9364:a775? ([2001:b07:6468:f312:d43d:6da3:9364:a775]) by smtp.gmail.com with ESMTPSA id w14sm2975048wrt.59.2019.06.07.11.22.36 (version=TLS1_3 cipher=AEAD-AES128-GCM-SHA256 bits=128/128); Fri, 07 Jun 2019 11:22:37 -0700 (PDT) Subject: Re: [patch 0/3] cpuidle-haltpoll driver (v2) To: Marcelo Tosatti , "Rafael J. Wysocki" Cc: kvm-devel , =?UTF-8?B?UmFkaW0gS3LDhD9tw4PCocOFPw==?= , Andrea Arcangeli , Peter Zijlstra , Wanpeng Li , Konrad Rzeszutek Wilk , Raslan KarimAllah , Boris Ostrovsky , Ankur Arora , Christian Borntraeger , Linux PM References: <20190603225242.289109849@amt.cnet> <6c411948-9e32-9f41-351e-c9accd1facb0@intel.com> <20190607171645.GA28275@amt.cnet> From: Paolo Bonzini Message-ID: <9c3853cc-d920-03e8-245c-86c33b280c80@redhat.com> Date: Fri, 7 Jun 2019 20:22:35 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190607171645.GA28275@amt.cnet> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 07/06/19 19:16, Marcelo Tosatti wrote: > There is no "target residency" concept in the virtualized use-case > (which is what poll_state.c uses to calculate the poll time). Actually there is: it is the cost of a vmexit, and it be calibrated with a very short CPUID loop (e.g. run 100 CPUID instructions and take the smallest TSC interval---it should take less than 50 microseconds, and less than a millisecond even on nested virt). I think it would make sense to improve poll_state.c to use an adaptive algorithm similar to the one you implemented, which includes optionally allowing to poll for an interval larger than the target residency. Paolo