From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-x236.google.com (mail-pf0-x236.google.com [IPv6:2607:f8b0:400e:c00::236]) by lists.bufferbloat.net (Postfix) with ESMTPS id 8040A3B2A0 for ; Tue, 5 Jan 2016 19:53:09 -0500 (EST) Received: by mail-pf0-x236.google.com with SMTP id e65so175888994pfe.1 for ; Tue, 05 Jan 2016 16:53:09 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=networkplumber-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:in-reply-to:references :mime-version:content-type:content-transfer-encoding; bh=1QhCMTbNjeSw2OAI/o/VWtmSOHG0mcGfhC5bPNdQ5EQ=; b=1nsrtWSqW1tuXzN8aW03+SfiO/mIJ9G/sRt+0TCCXr8CgbgOgFw/rahpVl/dTKWXBW KpDvOBPJ71wSNzU6vtEBfjM6+WwZP55NvRZAQxktOByPi62pNfbxe5mkOA8GyhUt/bm5 dfV5hbqVPZh4nXeXl/nXyYz2wLvUXX0IBeE5Jx2QOd7AhGeegTjeCWPLXK+ItpRo8NSm TNfRTe6Wu1cYk+ougSLyeoTVM5f+TOcDnury7kilYoHiMNP/QqlIrcRh3K0bfzkuxx7f nXESeB0xSj4r1NhJFseWkTD5vCQF4oDRpbOrE5uEK1lcaFHGpYujAlKN1/8gSR6IytUc a81Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:date:from:to:cc:subject:message-id:in-reply-to :references:mime-version:content-type:content-transfer-encoding; bh=1QhCMTbNjeSw2OAI/o/VWtmSOHG0mcGfhC5bPNdQ5EQ=; b=JZgJuE8/96QwBQQu+MQneJNJU2ujqZ1NKzVPxrAdWK8ojD94OqVcz4lOYhyBPxMqbS HJTcuDtxY5wND6iE4koBECNTS9Ffnh/XQfQvoTv+LcQFn4d+frpeQJv2a9Sb5yKeZCX5 sEUO5cmdvK1csdk/nP9tdQhOxCCYkCin8K1q8lVouKzGeDCfUvm+CrfvuxDa+eUfzw+U g928UEMtz4w6xM+erCp0Nd+HjNyVO09oA98AnSiBZ4Vgz8ugmWSS2atxhK5w2N++hYsg zSFyZI9G38xAzphx1vjIQuUNyUsKWXG7n4tq7HEz6WFCbiMTyUIHzS7/OI6BafZWrhlL Wg6Q== X-Gm-Message-State: ALoCoQk9LAGwSrIkvYgFb5ahMgnr09BB4Uwch9sHHbesz9/tzTlUCL8jf4I0DlS5Ez3xR6PvDzfOp7Y2LDPZkPZex4NUHsbLHg== X-Received: by 10.98.65.219 with SMTP id g88mr123285727pfd.63.1452041586659; Tue, 05 Jan 2016 16:53:06 -0800 (PST) Received: from xeon-e3 (static-50-53-82-155.bvtn.or.frontiernet.net. [50.53.82.155]) by smtp.gmail.com with ESMTPSA id wa17sm67438953pac.38.2016.01.05.16.53.05 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 05 Jan 2016 16:53:06 -0800 (PST) Date: Tue, 5 Jan 2016 16:53:14 -0800 From: Stephen Hemminger To: "Steinar H. Gunderson" Cc: "bloat@lists.bufferbloat.net" Message-ID: <20160105165314.118713f3@xeon-e3> In-Reply-To: <20160106002213.GA8486@sesse.net> References: <165DB6E9-A6DD-4626-B6AA-E1B2DBA0B5FA@gmail.com> <568C1209.5050403@taht.net> <20160106000151.GA5332@sesse.net> <20160106002213.GA8486@sesse.net> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: [Bloat] Hardware upticks X-BeenThere: bloat@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: General list for discussing Bufferbloat List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 06 Jan 2016 00:53:09 -0000 On Wed, 6 Jan 2016 01:22:13 +0100 "Steinar H. Gunderson" wrote: > On Tue, Jan 05, 2016 at 04:06:03PM -0800, Stephen Hemminger wrote: > > The expensive part is often having to save and restore all the state in > > registers and other bits on context switch. > > Are you sure? There's not really all that much state to save, and all I've > been taught before says the opposite. > > Also, I've never ever seen the actual context switch turn up high in a perf > profile. Is this because of some sampling artifact? Yes, especially with Intel processors getting more and more SSE/floating point registers.