From owner-freebsd-questions@FreeBSD.ORG Fri Jan 18 15:39:57 2013 Return-Path: Delivered-To: questions@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 81EDD2F3 for ; Fri, 18 Jan 2013 15:39:57 +0000 (UTC) (envelope-from lists@eitanadler.com) Received: from mail-la0-f46.google.com (mail-la0-f46.google.com [209.85.215.46]) by mx1.freebsd.org (Postfix) with ESMTP id 0BD64F9 for ; Fri, 18 Jan 2013 15:39:56 +0000 (UTC) Received: by mail-la0-f46.google.com with SMTP id fq12so1518881lab.5 for ; Fri, 18 Jan 2013 07:39:55 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=eitanadler.com; s=0xdeadbeef; h=x-received:mime-version:in-reply-to:references:from:date:message-id :subject:to:cc:content-type; bh=hZ1eRdu3ro0ySMNwC6QBBKndwyicUV2xkO4BQMGev2k=; b=W9RvbVL0XBqOq/ybc0b0SX/+H1XPhED8ROmxmU59M2H2hRfuxVv0KRcDNz07kaTKxj gyIrRtOvRKqQk3nQt6lRC3yzKC9/01mh/Fi3ElqjVi024uhPhezd8i8T7+r+ddhGE+kP BZRp8QPhW62BxxERQYItwtde++5N02goFcB40= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20120113; h=x-received:mime-version:in-reply-to:references:from:date:message-id :subject:to:cc:content-type:x-gm-message-state; bh=hZ1eRdu3ro0ySMNwC6QBBKndwyicUV2xkO4BQMGev2k=; b=aCiYhkcsp8xbTSTZ1qQ12SOOJRQ+NsgNLuSv931igjCkl4oCABC7L8I/3ubCSBD4x5 TSV/ohURuvjC3mifl7DxCsd8b3emqI7iWlw9zsnepyS8HEFUCoHXtEb/61Kwz0uabtXu Qc6/rvT64VzN+8H7vIUg4PzVp4SmYaRCz4MA4tQbBw1Byn7g8TxFDxD4E8XkX9mKEz3R vDmhHzS0xdPw0Erw7lje5OkbI+Fo6RlIemUoRD4VdUZl3B/n25CT88BccAdJImo0eA0K nVn46L2PIG55AkmEKQ6EVob56T8n1XbrufuvEmqbH4AjuYgtFhlh13gEjHISwl3yFSEq h2pA== X-Received: by 10.152.144.4 with SMTP id si4mr8815012lab.10.1358523595308; Fri, 18 Jan 2013 07:39:55 -0800 (PST) MIME-Version: 1.0 Received: by 10.112.30.131 with HTTP; Fri, 18 Jan 2013 07:39:25 -0800 (PST) In-Reply-To: <20130118112010.43ad3edb@fabiankeil.de> References: <20130117135241.434f273a@fabiankeil.de> <20130118112010.43ad3edb@fabiankeil.de> From: Eitan Adler Date: Fri, 18 Jan 2013 10:39:25 -0500 Message-ID: Subject: Re: absurd I/O perf with ZFS: hangs on zfs->cv) To: Fabian Keil Content-Type: text/plain; charset=UTF-8 X-Gm-Message-State: ALoCoQnm0L/WHOtNCKtihvcnqlOVsGMJ4TCmS9GswzDfnQ5kkVCQX4TOay9gR2PkKCd3RJDOJc0I Cc: questions@freebsd.org X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 18 Jan 2013 15:39:57 -0000 On 18 January 2013 05:20, Fabian Keil wrote: > A common recommendation is to disable atime for all datasets where > it isn't needed as it can cause lots of unnecessary write operations. Good call. I thought I had already disabled atime updating but it turns out that some datasets had this property still on. > With 8 GB of RAM ZFS enables prefetching by default and I assume > for the git use case it's not too useful and could hurt performance > by amplifying read operations. The "Data Prefetch Efficiency" is > shown by zfs-stats and if it doesn't look too impressive you might > want to disable prefetching to see if it helps. I will look at this number - thanks. > If your repository isn't fresh, you could also try "git gc". > My impression is that the automatic doesn't trigger frequently > enough for larger repositories like /usr/src. This isn't git specific. Doing anything remotely I/O related takes forever: - starting a new shell take over a minute - opening a file in vim which wasn't opened recently take a few minutes - etc. That said, I will be looking closely at the zfs-stats and see if I notice any patterns. -- Eitan Adler