From owner-freebsd-arm@freebsd.org Thu Jun 9 14:40:55 2016 Return-Path: Delivered-To: freebsd-arm@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 EC090B6F945 for ; Thu, 9 Jun 2016 14:40:55 +0000 (UTC) (envelope-from ian@freebsd.org) Received: from outbound1b.ore.mailhop.org (outbound1b.ore.mailhop.org [54.200.247.200]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id B47711712 for ; Thu, 9 Jun 2016 14:40:55 +0000 (UTC) (envelope-from ian@freebsd.org) X-MHO-User: 301efb0c-2e50-11e6-a0ff-e511cd071b9b X-Report-Abuse-To: https://support.duocircle.com/support/solutions/articles/5000540958-duocircle-standard-smtp-abuse-information X-Originating-IP: 73.34.117.227 X-Mail-Handler: DuoCircle Outbound SMTP Received: from ilsoft.org (unknown [73.34.117.227]) by outbound1.ore.mailhop.org (Halon Mail Gateway) with ESMTPSA; Thu, 9 Jun 2016 14:41:01 +0000 (UTC) Received: from rev (rev [172.22.42.240]) by ilsoft.org (8.15.2/8.14.9) with ESMTP id u59EelfG004091; Thu, 9 Jun 2016 08:40:47 -0600 (MDT) (envelope-from ian@freebsd.org) Message-ID: <1465483247.1188.60.camel@freebsd.org> Subject: Re: RPi2 i/o blocking and SD card performance From: Ian Lepore To: Warner Losh , Gergely Imreh Cc: FreeBSD ARM Date: Thu, 09 Jun 2016 08:40:47 -0600 In-Reply-To: <6406AECE-0153-494F-88EE-E58C8357FC1B@bsdimp.com> References: <6406AECE-0153-494F-88EE-E58C8357FC1B@bsdimp.com> Content-Type: text/plain; charset="iso-8859-13" X-Mailer: Evolution 3.16.5 FreeBSD GNOME Team Port Mime-Version: 1.0 Content-Transfer-Encoding: 8bit X-BeenThere: freebsd-arm@freebsd.org X-Mailman-Version: 2.1.22 Precedence: list List-Id: "Porting FreeBSD to ARM processors." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 09 Jun 2016 14:40:56 -0000 On Thu, 2016-06-09 at 09:55 -0400, Warner Losh wrote: > > On Jun 9, 2016, at 5:37 AM, Gergely Imreh wrote: > > > > Hi, > > > > I've been testing FreeBSD 11.0-CURRENT on a RaspberryPi2. I'm relatively > > new to FreeBSD, and wondering if there's any advice for improving the > > performance a bit. > > > > First, it looks like there's a lot of i/o blocking behaviour going on. For > > example running MediaWiki on the board, if I compile any ports, the site > > itself is pretty much unusable (the PHP scripts time out even with 180s > > timeouts). The strangest thing is that the CPU usage is not at 100% all the > > way, can be that all 4 cores are ~99% idle, and still everything goes very > > slow. Once the ports compilation or any other i/o-related task is finished, > > it's snappy again. > > > > Any idea why it could be to have such big latency/lag even though the CPU > > is idle? Is there anything I could test? > > Whatÿs the HZ for the system? The sd/mmc system has a lot of context switches > may be one reason for this. What does HZ have to do with it? That's a serious question I've been asking for about 3 years now, and have not gotten an answer (any answer from anyone): "What influence does HZ have on modern freebsd?" (Modern meaning roughly "with eventtimers implemented and the ULE scheduler.") The little bit of testing I've tried to do hasn't shown any difference at all that I can detect between HZ=100 and HZ=5000, or any values inbetween. -- Ian