From owner-freebsd-current@FreeBSD.ORG Sun Mar 21 14:04:13 2010 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 405D11065673; Sun, 21 Mar 2010 14:04:13 +0000 (UTC) (envelope-from mavbsd@gmail.com) Received: from fg-out-1718.google.com (fg-out-1718.google.com [72.14.220.158]) by mx1.freebsd.org (Postfix) with ESMTP id 8E77E8FC15; Sun, 21 Mar 2010 14:04:12 +0000 (UTC) Received: by fg-out-1718.google.com with SMTP id d23so157839fga.13 for ; Sun, 21 Mar 2010 07:04:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:sender:message-id:date:from :user-agent:mime-version:to:cc:subject:references:in-reply-to :x-enigmail-version:content-type:content-transfer-encoding; bh=PrrFva0kbQYNEA6MUrI01eUuqXd4VQBIKirXR/fKBj4=; b=d3VbPi3SyUt/Q7szCjvpA+EBTqdOpWJtRKCj0TxnUfoUgX53r4MSnEweoStSnvXRAJ 05iTulqA0CyEWNaq2qvhdLUMJkrPd2rrK//TAL/4qfel0zlPhre05ILXoez4TXbJKp+Q l3hFfc9kCgOgBRpjAnyAjjwgwveSeK74Xa2v4= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=sender:message-id:date:from:user-agent:mime-version:to:cc:subject :references:in-reply-to:x-enigmail-version:content-type :content-transfer-encoding; b=njKgfKaDyDThztxFPemi0xSFgbR2fLi5MWzlnEsckerPTzlYj6CgrPBMc91NvcPdU2 wrzL01tQLdlBj9hnNP7+2DoYhMELKQpo3UZWyFc9KAVjLSPjHRKtHugOyPVuVLZZl9QW MjzjPhXVU7wPII9xEnvg2n3IcgtOXuJCVrdak= Received: by 10.87.62.1 with SMTP id p1mr4192349fgk.42.1269180251307; Sun, 21 Mar 2010 07:04:11 -0700 (PDT) Received: from mavbook.mavhome.dp.ua (pc.mavhome.dp.ua [212.86.226.226]) by mx.google.com with ESMTPS id 16sm920679fxm.0.2010.03.21.07.04.10 (version=SSLv3 cipher=RC4-MD5); Sun, 21 Mar 2010 07:04:10 -0700 (PDT) Sender: Alexander Motin Message-ID: <4BA62757.7090400@FreeBSD.org> Date: Sun, 21 Mar 2010 16:04:07 +0200 From: Alexander Motin User-Agent: Thunderbird 2.0.0.23 (X11/20091212) MIME-Version: 1.0 To: Julian Elischer References: <4BA4E7A9.3070502@FreeBSD.org> <201003201753.o2KHrH5x003946@apollo.backplane.com> <891E2580-8DE3-4B82-81C4-F2C07735A854@samsco.org> <4BA52179.9030903@FreeBSD.org> <4BA532FF.6040407@elischer.org> In-Reply-To: <4BA532FF.6040407@elischer.org> X-Enigmail-Version: 0.96.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: FreeBSD-Current , freebsd-arch@freebsd.org Subject: Re: Increasing MAXPHYS X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 21 Mar 2010 14:04:13 -0000 Julian Elischer wrote: > In the Fusion-io driver we find that the limiting factor is not the > size of MAXPHYS, but the fact that we can not push more than > 170k tps through geom. (in my test machine. I've seen more on some > beefier machines), but that is only a limit on small transacrtions, > or in the case of large transfers the DMA engine tops out before a > bigger MAXPHYS would make any difference. Yes, GEOM is quite CPU-hungry on high request rates due to number of context switches. But impact probably may be reduced from two sides: by reducing overhead per request, or by reducing number of requests. Both ways may give benefits. If common opinion is not to touch defaults now - OK, agreed. (Note, Scott, I have agreed :)) But returning to the original question, does somebody knows real situation when increased MAXPHYS still causes problems? At least to make it safe. -- Alexander Motin