From owner-freebsd-stable@FreeBSD.ORG Sat Mar 21 16:31:03 2015 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 4F95CEF5; Sat, 21 Mar 2015 16:31:03 +0000 (UTC) Received: from mail-ig0-x229.google.com (mail-ig0-x229.google.com [IPv6:2607:f8b0:4001:c05::229]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 0FFD9A04; Sat, 21 Mar 2015 16:31:03 +0000 (UTC) Received: by igcau2 with SMTP id au2so8922680igc.1; Sat, 21 Mar 2015 09:31:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:sender:in-reply-to:references:date:message-id:subject :from:to:cc:content-type; bh=3vU1JoKMYvmyO1BmF35Cs7X8C706tdq90b4AJ8cz7JQ=; b=u7AEDLLqPXVF6rUY9MoobrA2IKzMVZD7AtgYEgaEvFgf1Z2y4jTa2yUJE4kzEwwQYf T7MrdxLQjRz3byM/iu6M6zdx/zzvWDbzMKBIMaRePRX8//kY1nC0K1u6wkr+beTNxxr4 f5gaiDHyUh08xvPYGiNJPs1m48C6gHmcoU6IJz9ZM36Ash4DVAZdYI4wWkHcB6jS2bWQ 1ge4AcRfXjSn92Au74qh61CPYHdX68oNOcGjtfMfr7PyVWn4s3X2ioxC6EHdO6q+n2dO QZfaGULSfNv8qnkpZ3JHAhBuBkx+wy/NVZJdzP3HoZLtRXtezLubbzwUzz/Uy8USAgB8 IJow== MIME-Version: 1.0 X-Received: by 10.107.155.13 with SMTP id d13mr153297730ioe.29.1426955462556; Sat, 21 Mar 2015 09:31:02 -0700 (PDT) Sender: adrian.chadd@gmail.com Received: by 10.36.17.194 with HTTP; Sat, 21 Mar 2015 09:31:02 -0700 (PDT) In-Reply-To: <550D93C7.9080709@FreeBSD.org> References: <5506250A.2000506@sentex.net> <20150316132055.GQ32288@funkthat.com> <5509D6C6.4050204@sentex.net> <20150318211457.GL51048@funkthat.com> <550B6950.8060806@sentex.net> <550C5AAF.9060502@sentex.net> <550C8AEE.4090408@sentex.net> <550CB306.7030405@delphij.net> <20150321001559.GB2379@kib.kiev.ua> <550CBF80.6030809@sentex.net> <550D93C7.9080709@FreeBSD.org> Date: Sat, 21 Mar 2015 09:31:02 -0700 X-Google-Sender-Auth: zVC5a-wFhjQX1Z9iYPYInF1enwA Message-ID: Subject: Re: RELENG_10 performance regression (was Re: 35-40% performance drop releng9 vs releng10 openvpn From: Adrian Chadd To: John Baldwin Content-Type: text/plain; charset=UTF-8 Cc: Konstantin Belousov , FreeBSD-STABLE Mailing List , John-Mark Gurney , Xin LI X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 21 Mar 2015 16:31:03 -0000 On 21 March 2015 at 08:52, John Baldwin wrote: > On 3/20/15 8:46 PM, Mike Tancsa wrote: >> On 3/20/2015 8:15 PM, Konstantin Belousov wrote: >>>> >>>> For the purpose of devfs, does it make sense to bump timestamps like >>>> normal filesystems for each read/write operation? Looks like Mac OS X >>>> will bump timestamps for each operation but Debian don't. >>> >>> First question is, what timecounter hardware is used. I would accept >>> some slowdown from hardware like HPET, but it is indeed surprising >>> if caused by TSC. >>> >>> >> >> David Wolfskill suggested trying the problem commit with >> >> vfs.timestamp_precision=0 >> >> and it does indeed restore performance to what it was. The raw dtrace >> files are available and FlameGraphs can all be found at >> >> http://tancsa.com/time/ > > Do you know why you are using the HPET instead of TSC for timestamping? > Using the TSC can make a non-trivial performance difference since userland > can calculate timestamps without using system calls when it is used. > (That is not related to this case, but switching to the TSC in general is > preferable.) > > There are a few generations of Intel CPUs where you can't mix deeper sleep > states with the TSC as timecounter, but those CPUs are getting to be a bit > older at this point. What about various VMs? -adrian