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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 9394FC43603 for ; Thu, 19 Dec 2019 09:23:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 64BA02465E for ; Thu, 19 Dec 2019 09:23:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="IkiMFE+I" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726622AbfLSJXf (ORCPT ); Thu, 19 Dec 2019 04:23:35 -0500 Received: from merlin.infradead.org ([205.233.59.134]:44892 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726620AbfLSJXe (ORCPT ); Thu, 19 Dec 2019 04:23:34 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=24GBdvgPOniGO/u5Izbxbzv5IyyCWf616Is9oo5bboE=; b=IkiMFE+IcFYckiwO+I/fcf1MJ r6UTOjpgng6pF5rYTgTYW6LqO+2AuIP+72yCDVZn73fuJlkJXE+Z8hQzqr/12NibItH+SdwR/1WW1 I4wcDCWItTYlUOM3tMIc1Jh64if4MsvSu/aHkGQYztIf+dXOo8BoWyBMtKZVlFO42eaDS4qXJ1sBG oymRrm1w76EZlnzrH5druTNPIWF5i6oCrYykaUKX9xruroRn1PDyXftHdj2y4rX0W0EtsOTAmxReL YPWDMtK4iEfJ1qyq6chSQe33ZCpwIPrnRGclYpObEkKYbd5qoTT8v3PFakpC9E/j1V1WedcUnbX6f aairSL9qw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1ihs1h-0005cs-0B; Thu, 19 Dec 2019 09:23:21 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 1EF64304D00; Thu, 19 Dec 2019 10:21:56 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 949ED2B291C41; Thu, 19 Dec 2019 10:23:19 +0100 (CET) Date: Thu, 19 Dec 2019 10:23:19 +0100 From: Peter Zijlstra To: Ming Lei Cc: Thomas Gleixner , Jens Axboe , linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, Long Li , Ingo Molnar , Christoph Hellwig , Keith Busch , Sagi Grimberg , John Garry , Hannes Reinecke Subject: Re: [RFC PATCH 2/3] softirq: implement interrupt flood detection Message-ID: <20191219092319.GX2844@hirez.programming.kicks-ass.net> References: <20191218071942.22336-1-ming.lei@redhat.com> <20191218071942.22336-3-ming.lei@redhat.com> <20191218104941.GR2844@hirez.programming.kicks-ass.net> <20191219015948.GB6080@ming.t460p> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191219015948.GB6080@ming.t460p> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Thu, Dec 19, 2019 at 09:59:48AM +0800, Ming Lei wrote: > > So pray tell, why did you not integrate this with IRQ_TIME_ACCOUNTING ? > > That already takes a timestamp and does most of what you need. > > Yeah, that was the 1st approach I thought of, but IRQ_TIME_ACCOUNTING > may be disabled, and enabling it may cause observable effect on IO > performance. Is that an actual concern, are people disabling it? > > > @@ -356,6 +512,7 @@ void irq_enter(void) > > > } > > > > > > __irq_enter(); > > > + irq_interval_update(); > > > } > > > > Arggh.. you're going to make every single interrupt take at least 2 > > extra cache misses for this gunk?!? > > Could you explain it a bit why two cache misses are involved? > > I understand at most one miss is caused, which should only happen in > irq_interval_update(), and what is the other one? The rq clock thing IIRC.