From owner-freebsd-hackers@freebsd.org Tue Sep 15 22:34:47 2015 Return-Path: Delivered-To: freebsd-hackers@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 822009CD9A6 for ; Tue, 15 Sep 2015 22:34:47 +0000 (UTC) (envelope-from jim@netgate.com) Received: from mail-ob0-x22f.google.com (mail-ob0-x22f.google.com [IPv6:2607:f8b0:4003:c01::22f]) (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 4FEB91F13 for ; Tue, 15 Sep 2015 22:34:47 +0000 (UTC) (envelope-from jim@netgate.com) Received: by obbbh8 with SMTP id bh8so147775991obb.0 for ; Tue, 15 Sep 2015 15:34:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=netgate.com; s=google; h=content-type:mime-version:subject:from:in-reply-to:date:cc :message-id:references:to; bh=8Pw11p5+QtfpIjZDWwqcsOdqtUvUhJ1X3jXp4g/aR9Y=; b=nL6oRZQY89VzRjI1a6Im+KreK6Z6EvZlDTgAMdbUZTLA0slGFZuSc8QAUWXL5AnNhC KRWYIiOverCDq2s49B0TJyPvrZblyuqcUsOVXYutapi9WwFcrX7pt1nBCXMmZVhOWXfN oAFlEYJbAAVJnB+8alLby2YrwtoThVsMSWzvA= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:content-type:mime-version:subject:from :in-reply-to:date:cc:message-id:references:to; bh=8Pw11p5+QtfpIjZDWwqcsOdqtUvUhJ1X3jXp4g/aR9Y=; b=VvCTvkeuA5vn4mmdX2gHJAbaXqKO18O36JSvgLcRodREoOvsVTPC+pmMRWSYOZX5jE 4fZHuxczoRY6iUP94zxEY0Ks8DrXOm6BGQYotxTDTRao/m+n8e9sI6CeHD0fWBMFUDPG j4m3TmZNL1shDj9z5JVcJgwVMWIMo3eJ7Ay8Ryw5DdgEHEug4Nh3JVG2l6Gl+OZbRhi+ sY+KPZUBYD3au2/FN+xCovmsbl8v6zb5k/KghnkJUy/A+58VQKuEmfSc3w42xhb4/mLO PayD3flNPaE7FXSiklep3y7rdXrHSsbvkGGSbobpG6J27VqHEgPodeKrdwj/4zBOfDpC u1OA== X-Gm-Message-State: ALoCoQn52l0Ky3OsCAeCtMM8Wpjr9WLU60CYkB3tw5dyZZ73ZOxBZtBn0GeOVj16mhqgZykuFLu6 X-Received: by 10.60.142.170 with SMTP id rx10mr20567897oeb.28.1442356486530; Tue, 15 Sep 2015 15:34:46 -0700 (PDT) Received: from ?IPv6:2610:160:11:33:343f:2e55:fcb2:6efb? ([2610:160:11:33:343f:2e55:fcb2:6efb]) by smtp.gmail.com with ESMTPSA id dc9sm9705080obb.17.2015.09.15.15.34.45 (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Tue, 15 Sep 2015 15:34:46 -0700 (PDT) Mime-Version: 1.0 (Mac OS X Mail 8.2 \(2104\)) Subject: Re: ECC support From: Jim Thompson In-Reply-To: Date: Tue, 15 Sep 2015 17:34:44 -0500 Cc: Dieter BSD , Hackers freeBSD , freebsd-hardware@freebsd.org Message-Id: <8435FBF3-2F8E-4A25-ABEA-B7038AFFE372@netgate.com> References: <41EFCF21-D3B0-4EC4-8EAB-417CA33821FC@netgate.com> To: Igor Mozolevsky X-Mailer: Apple Mail (2.2104) Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Content-Filtered-By: Mailman/MimeDel 2.1.20 X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 15 Sep 2015 22:34:47 -0000 > On Sep 15, 2015, at 5:19 PM, Igor Mozolevsky = wrote: >=20 > On 15 September 2015 at 22:52, Jim Thompson > wrote: >=20 > >=20 > Errors are corrected "on-the-fly," corrected data is almost never = placed back in memory. If the same corrupt data is read again, the = correction process is repeated. Replacing the data in memory would = require processing overhead that could accumulate and significantly = diminish system performance. If the error occurred because of random = events and isn't a defect in the memory, the memory address will be = cleaned of the error when the data is overwritten with other data. >=20 > =20 >=20 > Just to correct a small oversight- most (if not all?) boards have an = option to scrub ECC memory in the background so as to prevent single bit = (recoverable) errors from turning into double bit (irrecoverable but = detectable) errors ;-) I think you=E2=80=99ll find that the default for =E2=80=98scrub=E2=80=99 = is off on most (perhaps all) boards. There are reasons, and these = relate directly to =E2=80=9Csignificantly diminish system = performance=E2=80=9D, (above), as well as the greatly increased RAM = sizes in use today. =E2=80=99Scrub' was popular about a decade ago, when DDR2 RAM was around = $100/GB. DDR3-1600 is about $6/GB today. Jim