From owner-freebsd-hackers@FreeBSD.ORG Tue Sep 14 12:40:39 2010 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 15E16106564A for ; Tue, 14 Sep 2010 12:40:39 +0000 (UTC) (envelope-from cronfy@gmail.com) Received: from mail-bw0-f54.google.com (mail-bw0-f54.google.com [209.85.214.54]) by mx1.freebsd.org (Postfix) with ESMTP id 99F4C8FC13 for ; Tue, 14 Sep 2010 12:40:38 +0000 (UTC) Received: by bwz15 with SMTP id 15so231136bwz.13 for ; Tue, 14 Sep 2010 05:40:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:mime-version:received:in-reply-to :references:from:date:message-id:subject:to:content-type :content-transfer-encoding; bh=xIRs/8CLMx8Y6X31HRmvyrj3QNuwH7F6hIElIkaBp0Y=; b=bNbc8aCm77SStPdXFmHM/cEfo2mKUeltWVUmQHtf5fZSAsG/HtXkjmNO6yw9FPWMXv z1BQBZ4/lRENjNzzp+1LERD0UU/CnClk7rew5Xe3hW4Pno/3d+yi9kMIq+WAtJcCBsM3 1njqhGIqmcMGYmBFlgf6N6XdMRsceN2c96WuM= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :content-type:content-transfer-encoding; b=JHwDqRtikl5IiURjofoeZ+73i/TM9P+/9k/wfdkVDbDr95eNDkv8/FhT8cweXl82Kg Milw81+HT8Svb9mKoaIwb6oXbswnZPCi7QR0G7GOIP20nqr/ZKU0I0lr2W9qUgw6XzKu 1lFSb7eVhhwG01Oq/4D4foSNpm46d4KgwvnhE= Received: by 10.204.76.140 with SMTP id c12mr4388021bkk.7.1284468037314; Tue, 14 Sep 2010 05:40:37 -0700 (PDT) MIME-Version: 1.0 Received: by 10.204.99.197 with HTTP; Tue, 14 Sep 2010 05:40:07 -0700 (PDT) In-Reply-To: References: From: cronfy Date: Tue, 14 Sep 2010 16:40:07 +0400 Message-ID: To: freebsd-hackers@freebsd.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Subject: Re: is vfs.lookup_shared unsafe in 7.3? X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 14 Sep 2010 12:40:39 -0000 >> Trying to overtake high server load (sudden peaks of 15%us/85%sy, LA> >> 40, very slow lstat() at these moments, looks like some kind of lock >> contention) I enabled vfs.lookup_shared=3D1 on two servers today. One is >> FreeBSD-7.3 kernel csup'ed and built Sep =A09 2010 and other is >> FreeBSD-7.3 csup'ed and built Jul 16 2010. > > The important think you missed is *where* is the supposed lock contention= . > If you have lots of processes in "ufs" state, there are other things that > can help you, such as increasing vfs.ufs.dirhash_maxmem. Before I changed vfs.lookup_shared I did increase vfs.ufs.dirhash_maxmem to 16M. It filled in ~5 minutes, but even while it was not full, server was not running better. Usually there is very small number of processes in ufs state (they are even not in top). That processes I've been talking about I suspect were the consequence of enabling vfs.lookup_shared. I also enabled hwpmc to examine system at the moments of high load, but did not have a chance to use it. What am I afraid of now is that server that is running nice till now may crash, that's why I am asking about stability of vfs.lookup_shared in 7.3. At svn.freebsd.org I see a couple of commits in stable/7/sys/fs/ and ufs/ for last 2 months that could change the behaviour, and this may be the reason why one system is running stable, and another was not. But I am not sure about it, so I am asking experienced people here :) --=20 // cronfy