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=-2.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 0EABCC5ACCC for ; Thu, 18 Oct 2018 09:05:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BC3B0208E4 for ; Thu, 18 Oct 2018 09:05:53 +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="rWx7GeRV" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BC3B0208E4 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727844AbeJRRFy (ORCPT ); Thu, 18 Oct 2018 13:05:54 -0400 Received: from merlin.infradead.org ([205.233.59.134]:40338 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727136AbeJRRFx (ORCPT ); Thu, 18 Oct 2018 13:05:53 -0400 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=EswSLoEMlBvoYgXbjoVLcGGXTkxK5K7C3pahk5Zvq+Y=; b=rWx7GeRVQkco22WsEx7Fq2hyg dXQegWpQTWi1137nExpsgyvf1QP63Dyzhn/17AlKuw55l7PVoDxeqBqwODHyjh4I8UUTvRtCKKWwT mYKcmWgsdPdDtirVrQ1TszTZXNSmV5cam0wM/s2XQyDyxvUUFAUjqFMCjPFiS3EgGczFwtBnwKAAN z4FRkKcJIQ1wq4i2T++Lly1NR6uDV0Zs1I3j6kGXESWDNmLv97crbzbxqBwW4vntqY18BhpnJrB/P qKTi344cUQfUVLAFQeF4JhWyXRky0ehA1vYWNHShgZ+5m1K619NqVVYOevPlid0U9l9pqpPfGn2g4 m78oBoJGw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1gD4FX-0003bH-Sk; Thu, 18 Oct 2018 09:05:48 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 47FAB2029856A; Thu, 18 Oct 2018 11:05:45 +0200 (CEST) Date: Thu, 18 Oct 2018 11:05:45 +0200 From: Peter Zijlstra To: Waiman Long Cc: Ingo Molnar , Will Deacon , linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] locking/qspinlock_stat: Count instances of nested lock slowpaths Message-ID: <20181018090545.GV3121@hirez.programming.kicks-ass.net> References: <1539697507-28084-1-git-send-email-longman@redhat.com> <20181017073833.GE3121@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 17, 2018 at 05:06:46PM -0400, Waiman Long wrote: > On 10/17/2018 03:38 AM, Peter Zijlstra wrote: > > On Tue, Oct 16, 2018 at 09:45:06AM -0400, Waiman Long wrote: > >> Queued spinlock supports up to 4 levels of lock slowpath nesting - > >> user context, soft IRQ, hard IRQ and NMI. However, we are not sure how > >> often the nesting happens. So 3 more per-cpu stat counters are added > >> to track the number of instances where nesting index goes to 1, 2 and > >> 3 respectively. > >> > >> On a dual-socket 64-core 128-thread Zen server, the following were stat > >> counter values under different circumstances. > >> > >> State slowpath index1 index2 index3 > >> ----- -------- ------ ------ ------- > >> After bootup 1,012,150 82 0 0 > >> After parallel build + perf-top 125,195,009 82 0 0 > > Would probably be good to check a network workload. > > Do you have any suggestion of what network workload? I usually don't > test on network related workload. Some netperf runs? Be sure to ask the network folks for 2 systems with at least 10GBe or something. > The only way to have a nesting level of 3 is when there is lock > contention in user context, soft IRQ and hard IRQ simultaneously which > is very rare, network should be able to trigger a lot of softirq and hardirqs, which is why I wondered if it could hit significant 3 levels. But yeah, I played around a bit, and couldn't get my index* numbers to move at all. I suppose we've gotten really good at avoiding lock contention for all the benchmarks we care about :-)