From owner-freebsd-arch@FreeBSD.ORG Thu Feb 26 00:18:22 2015 Return-Path: Delivered-To: freebsd-arch@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 CB4E5200 for ; Thu, 26 Feb 2015 00:18:22 +0000 (UTC) Received: from mail-pa0-f54.google.com (mail-pa0-f54.google.com [209.85.220.54]) (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 997FD10D for ; Thu, 26 Feb 2015 00:18:22 +0000 (UTC) Received: by paceu11 with SMTP id eu11so9224668pac.10 for ; Wed, 25 Feb 2015 16:18:15 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:sender:subject:mime-version:content-type:from :in-reply-to:date:cc:message-id:references:to; bh=3O2r3Gy2W4/yrfRaFn33+YJ54Zem4RfAzJuwpWI67Zg=; b=XGJw/oDYeXZqp6EY6Oif+fGiXbsjdzpkoNWL+dCJgYTADb/L4v9Mgbn9GQ/uVNJ1PE D4a8/rzXvbjHGoNkbr5jaelH61cZSeLw/vPt+okS2fv1O4elpO4T74yaj7Yzip+so1Dw za3rCEjk6xfnPmgXp2nhX8Iy0JqliyZM/0OIyPOV6VYWNcZBChaOvYSx4t0ERjQ0C6Wf 8Uf+DZgWWtI1yz3GETqeCPDhMsAugbOMV4i9ipLWXUhNSdWcLzB7FuazE2EUSrnzzgiQ +yJ86GupiVw0eBtAffZJtZhAy6Hz/W/zk8xmfXcB180bC5bno6rO9uyA3LfHvks9hCVe DZxg== X-Gm-Message-State: ALoCoQkpiaHz3ZvKUSGGCRePNAIhdAG1ZN3ba2GXdz7ZQcArbaB4wpzv4/vCWNwipIER0TRem3Mp X-Received: by 10.67.10.47 with SMTP id dx15mr9909009pad.139.1424909894329; Wed, 25 Feb 2015 16:18:14 -0800 (PST) Received: from [10.64.25.63] ([69.53.236.236]) by mx.google.com with ESMTPSA id qp4sm42379950pbc.63.2015.02.25.16.18.12 (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 25 Feb 2015 16:18:13 -0800 (PST) Sender: Warner Losh Subject: Re: locks and kernel randomness... Mime-Version: 1.0 (Mac OS X Mail 8.2 \(2070.6\)) Content-Type: multipart/signed; boundary="Apple-Mail=_CE406D6A-343F-4088-9141-E6CFE14BA61E"; protocol="application/pgp-signature"; micalg=pgp-sha512 X-Pgp-Agent: GPGMail 2.5b5 From: Warner Losh In-Reply-To: <1774232.7ZAkabLA24@ralph.baldwin.cx> Date: Wed, 25 Feb 2015 17:18:10 -0700 Message-Id: <871FF097-7372-4901-8202-003398B6ABE3@bsdimp.com> References: <54ED87E9.8030706@astrodoggroup.com> <20150225085659.GA74514@kib.kiev.ua> <1774232.7ZAkabLA24@ralph.baldwin.cx> To: John Baldwin X-Mailer: Apple Mail (2.2070.6) Cc: Konstantin Belousov , freebsd-arch@freebsd.org X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 26 Feb 2015 00:18:22 -0000 --Apple-Mail=_CE406D6A-343F-4088-9141-E6CFE14BA61E Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=utf-8 > On Feb 25, 2015, at 1:20 PM, John Baldwin wrote: >=20 > On Wednesday, February 25, 2015 10:56:59 AM Konstantin Belousov wrote: >> The cost of the proposed patch, of course, is not the several >> thousands of instructions in the rebalance. The problem with it is = the >> introduction of the new spinlock, which will be used in many places >> after the introduction. The cost of the new and often used spinlock = is >> the increase of both interrupt latency and interrupt handler jitter = and >> cpu switch jitter. >>=20 >> So neither buildworld timing, nor network throughput are adequate >> to estimate the change. It is system unresponsivness and loss of >> the realtime behaviour up to some degree. >>=20 >> I thought that it was obvious, at least after spinlocks were = mentioned, >> but apparently it is not, since proposals to measure the patch effect >> by benchmarking buildworld or passing the traffic are made. >=20 > +1 >=20 > The only thing I will add is that in general this makes the system = more > fragile and complex as well. Please just stay with a regular mutex = and change > the scheduler to not use random() (which seems to be in progress?). = I'm not > sure why we needed the extra 40 messages in this thread after that was > effectively said the first time. If you=E2=80=99d like to be helpful, please review = https://reviews.freebsd.org/D1968 Harrison Grundy wrote it, and I put it in phabricator for him while he = sorts out his own account. In a fit of passive aggressiveness, I=E2=80=99ve added everybody who = commented on this thread as reviewers, except Bruce and Harrison who don=E2=80=99t = have accounts yet. Warner --Apple-Mail=_CE406D6A-343F-4088-9141-E6CFE14BA61E Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename=signature.asc Content-Type: application/pgp-signature; name=signature.asc Content-Description: Message signed with OpenPGP using GPGMail -----BEGIN PGP SIGNATURE----- Comment: GPGTools - https://gpgtools.org iQIcBAEBCgAGBQJU7mZCAAoJEGwc0Sh9sBEA3VsP/iNIgP9IbRVC8ZYh2yUx/9fX PRLC4Iqsj2ZakIdPaP3YnRXHEmrwEN8l2G6Zcf/rtJu1EZojyhdzAwW8cgdh6kfj 2AWmR2IjEph3FLiFFo2endZTwFvdE2SBj34uda45xV2ow4q98UvdliOKE9+ba0z1 7eaOSXjqYY3J1mCETHxfEDc08lf1qiRwxVtN2QwaCmzH0/l7a9QgLFvgbbD4sxyh /zf8xvnUG9CAj7HxCFrBs3r9NkFE9ifx6SBZxxK2mycv/YZKHF4ESp3XUXngy31Y hsJjC/m2SQQlCmoV4tACZQ4wL7TqI9wobBejr0wUGV6pbdGGhhrdhxDsfQHnJb8v W4gRQCBAIbNvYztyPql0LZuSC2ZQftCSOW/KHel0eZnvbIS/+wUAbzgrQgt4U0Ps tf2nX73vVCOh7SiW09ybezpK71F9NDFiKfQmYYYzquYJ6v8gHigjBnSaZlrnh2IC iY2s69wB+Huge6v/VMg4HsoDD6tXpAtf9Z/D9Lv4Ona17aLW9EQi2F0CPXTskxfX BJauYUzGPMyMWxqU3rbCXGAAzSF4ybxC6QE+e9n2ag6JpErqH3BLX9Ck6jfUQplk 19AU1DPFvde9Qt5Agj+Qnnde8jMhOmfv071GjQLDNWnrWncQFG8xzwXzLCe6cUME OQ96bfjh5fjZi/Uwi744 =EXES -----END PGP SIGNATURE----- --Apple-Mail=_CE406D6A-343F-4088-9141-E6CFE14BA61E--