From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 29150 invoked by alias); 21 Apr 2011 23:46:14 -0000 Received: (qmail 29141 invoked by uid 22791); 21 Apr 2011 23:46:14 -0000 X-SWARE-Spam-Status: No, hits=-6.1 required=5.0 tests=AWL,BAYES_00,RCVD_IN_DNSWL_HI,SPF_HELO_PASS,T_RP_MATCHES_RCVD X-Spam-Check-By: sourceware.org Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Thu, 21 Apr 2011 23:45:51 +0000 Received: from int-mx02.intmail.prod.int.phx2.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id p3LNjow7029425 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Thu, 21 Apr 2011 19:45:50 -0400 Received: from [10.3.113.81] (ovpn-113-81.phx2.redhat.com [10.3.113.81]) by int-mx02.intmail.prod.int.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id p3LNjn3X006195; Thu, 21 Apr 2011 19:45:50 -0400 Message-ID: <4DB0C1AD.6080802@redhat.com> Date: Thu, 21 Apr 2011 23:46:00 -0000 From: Josh Stone User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.15) Gecko/20110307 Fedora/3.1.9-0.39.b3pre.fc14 Lightning/1.0b3pre Thunderbird/3.1.9 MIME-Version: 1.0 To: Jake Maul CC: William Cohen , systemtap@sourceware.org Subject: Re: Linux VFS cache hit rate script References: <4DAF3D59.7020609@redhat.com> <4DB0B049.8070806@redhat.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-IsSubscribed: yes Mailing-List: contact systemtap-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Post: List-Help: , Sender: systemtap-owner@sourceware.org X-SW-Source: 2011-q2/txt/msg00147.txt.bz2 On 04/21/2011 04:01 PM, Jake Maul wrote: > 2 dev: 0 devname: N/A > 762956 dev: 16 devname: N/A > 520 dev: 18 devname: N/A > 4183 dev: 22 devname: N/A > 4 dev: 23 devname: N/A > 1288 dev: 265289728 devname: dm-0 > 1 dev: 27 devname: N/A > 872 dev: 3 devname: N/A > 3094 dev: 5 devname: N/A > 380875 dev: 6 devname: N/A Oy - it's possible that the "dev" is meaningless (or means something different) when the name is returned "N/A" (bdev==0), so we may be caching noise as the index. Or in any case, caching "N/A" in so many different forms is not helpful. Would you be willing to try this modified function? function __find_bdevname:string(dev:long, bdev:long) { if (bdev == 0) return "N/A" if (dev in __devnames) return __devnames[dev] return __devnames[dev] = bdevname(bdev) } > Both this script and the cache-hit-rate.stp script generally die with > that error in 30 seconds or less. The data above is around 30 seconds > or so. > > That bizarrely long dev number might be relevant... or maybe that's > just a normal quirk of LVM? It's not so bizarre - kernel device numbers are (MAJOR<<20)|MINOR, so this turns out to be device 253,0. That also means all those low dev numbers have MAJOR==0, which I think supports my theory that they are not normal. Josh