From owner-freebsd-hackers@FreeBSD.ORG Sun Jun 2 12:16:38 2013 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by hub.freebsd.org (Postfix) with ESMTP id 0039447A for ; Sun, 2 Jun 2013 12:16:37 +0000 (UTC) (envelope-from utisoft@gmail.com) Received: from mail-ie0-x234.google.com (mail-ie0-x234.google.com [IPv6:2607:f8b0:4001:c03::234]) by mx1.freebsd.org (Postfix) with ESMTP id CAD471084 for ; Sun, 2 Jun 2013 12:16:37 +0000 (UTC) Received: by mail-ie0-f180.google.com with SMTP id b11so7726374iee.25 for ; Sun, 02 Jun 2013 05:16:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:sender:in-reply-to:references:from:date :x-google-sender-auth:message-id:subject:to:cc:content-type; bh=w1Eyc0Iz/XJFBGU9MibWaM9H3LatARS+87IGaL6f5HU=; b=JAOY+cnEgvoKKesyYyzLyRPmgNugGsIJZ6cIWBygfvBEjR7Cwd36c0BF2XX6MncaEj 3Iqtf9tyQmVSOh3M+JYjTwfLPFRt404HP8H0Dsb3KLJyktsTZ0gch/RXknyUjsmHbOWo 0sgnrey/WCBQ/IEhc2BDDXe0oS+K9j+REEsWd1TC/Eys90wXlyiY2PdvRzTOiZLDEQIf 8bZ7y+vZKSStV92vtJhfWAw2iZAwO/bRDTsiEXxSHk4++zXFZCcW3DsQCQ6mARH8R5iJ 0AcQV4x0tohLWIRZcpHoNlHd/7qE9sTyGmpzGlRKeARGM1a2Ux2wvztbQctKi4cxaxKb 5H6g== X-Received: by 10.50.178.198 with SMTP id da6mr5787871igc.49.1370175397422; Sun, 02 Jun 2013 05:16:37 -0700 (PDT) MIME-Version: 1.0 Sender: utisoft@gmail.com Received: by 10.64.71.101 with HTTP; Sun, 2 Jun 2013 05:16:07 -0700 (PDT) In-Reply-To: <20130602124127.6c3a847ea5ddb116a69d4814@yahoo.es> References: <20130602124127.6c3a847ea5ddb116a69d4814@yahoo.es> From: Chris Rees Date: Sun, 2 Jun 2013 13:16:07 +0100 X-Google-Sender-Auth: V51pV1vzpoayvt671IK3BuBFt08 Message-ID: Subject: Re: sed query To: Eduardo Morras Content-Type: text/plain; charset=ISO-8859-1 Cc: "freebsd-hackers@freebsd.org" X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 02 Jun 2013 12:16:38 -0000 On 2 June 2013 11:41, Eduardo Morras wrote: > On Fri, 31 May 2013 15:01:59 +0100 > Chris Rees wrote: > >> Hi all, >> >> I think I've discovered a strange behaviour of sed perhaps triggered >> by the length of a regex passed to it. I noticed that a certain >> expression I passed took a very long time, and suspected the usual >> backtracking loop, so I started trimming it... and discovered this: >> >> [crees@pegasus]~% time sed -ne "s,^BitchX-[0-9][^|]*[\|]/usr/por,," >> /var/db/pkg/INDEX-9 >> 4.699u 0.007s 0:04.70 99.7% 40+2733k 0+0io 0pf+0w >> [crees@pegasus]~% time sed -ne "s,^BitchX-[0-9][^|]*[\|]/usr/po,," >> /var/db/pkg/INDEX-9 >> 0.042u 0.000s 0:00.04 100.0% 48+3216k 0+0io 0pf+0w >> >> I've looked at the code, and can't from a brief glance figure out why >> a slightly longer regex makes such a difference-- does it start to >> split it? > > Perhaps second one uses memory cache data? Run both twice and show us the second times. > Nope, same. [crees@pegasus]~% time sed -ne "s,^BitchX-[0-9][^|]*[\|]/usr/por,," /var/db/pkg/INDEX-9 4.703u 0.007s 0:04.85 96.9% 40+2732k 210+0io 0pf+0w [crees@pegasus]~% time sed -ne "s,^BitchX-[0-9][^|]*[\|]/usr/por,," /var/db/pkg/INDEX-9 4.748u 0.007s 0:04.75 99.7% 40+2732k 0+0io 0pf+0w I also get the same on head; [crees@medusa]~% time sed -ne "s,^BitchX-[0-9][^|]*[\|]/usr/por,," /var/db/pkg/INDEX-10 7.813u 0.015s 0:07.96 98.2% 40+183k 0+0io 0pf+0w [crees@medusa]~% time sed -ne "s,^BitchX-[0-9][^|]*[\|]/usr/po,," /var/db/pkg/INDEX-10 0.070u 0.000s 0:00.07 100.0% 45+205k 0+0io 0pf+0w [crees@medusa]~% uname -a FreeBSD medusa 10.0-CURRENT FreeBSD 10.0-CURRENT #0 r250009: Thu May 30 10:11:16 BST 2013 root@medusa:/usr/obj/usr/src/sys/MEDUSA amd64 Chris