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=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, 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 3F5EEC43603 for ; Thu, 19 Dec 2019 01:29:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1585221D7D for ; Thu, 19 Dec 2019 01:29:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="QPlHRIHb" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726721AbfLSB3g (ORCPT ); Wed, 18 Dec 2019 20:29:36 -0500 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:57862 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726518AbfLSB3g (ORCPT ); Wed, 18 Dec 2019 20:29:36 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1576718974; 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: in-reply-to:in-reply-to:references:references; bh=4LhO4qnJS45ZijWda0VRuzykvBdUDahmQTHCJMOmgGs=; b=QPlHRIHbQjUaUS9DdNlALFjTRxw7T88lvqrmSDQeUxD3A/aQrxixAcRNLvXXqU38aAYhxZ VDwEgELfl3OiPP9oPGTX5alRLv0T/n4w/X6FXAw/tIIa1hxQRw/sq+fiNfBzaNgcn237jP dHNZOCU+PngC0PerSTEmKi/Z1+lefh8= 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-46-fS7bsj_0OvSazFPteXhE0Q-1; Wed, 18 Dec 2019 20:29:31 -0500 X-MC-Unique: fS7bsj_0OvSazFPteXhE0Q-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id DDB361854334; Thu, 19 Dec 2019 01:29:28 +0000 (UTC) Received: from ming.t460p (ovpn-8-22.pek2.redhat.com [10.72.8.22]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E894F5C28C; Thu, 19 Dec 2019 01:29:19 +0000 (UTC) Date: Thu, 19 Dec 2019 09:29:14 +0800 From: Ming Lei To: Peter Zijlstra Cc: Thomas Gleixner , Jens Axboe , linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, Long Li , Ingo Molnar , Keith Busch , Christoph Hellwig , Sagi Grimberg , John Garry , Hannes Reinecke Subject: Re: [RFC PATCH 1/3] sched/core: add API for exporting runqueue clock Message-ID: <20191219012914.GA6080@ming.t460p> References: <20191218071942.22336-1-ming.lei@redhat.com> <20191218071942.22336-2-ming.lei@redhat.com> <20191218095101.GQ2844@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191218095101.GQ2844@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Wed, Dec 18, 2019 at 10:51:01AM +0100, Peter Zijlstra wrote: > On Wed, Dec 18, 2019 at 03:19:40PM +0800, Ming Lei wrote: > > Scheduler runqueue maintains its own software clock that is periodically > > synchronised with hardware. Export this clock so that it can be used > > by interrupt flood detection for saving the cost of reading from hardware. > > But you don't have much, if any, guarantees the thing gets updated. Any software clock won't be guaranteed to be updated in time, however, they are still useful. Thanks, Ming