From owner-freebsd-questions@FreeBSD.ORG Mon Mar 28 02:42:35 2011 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 48A25106566B for ; Mon, 28 Mar 2011 02:42:35 +0000 (UTC) (envelope-from LukeD@pobox.com) Received: from sasl.smtp.pobox.com (a-pb-sasl-sd.pobox.com [64.74.157.62]) by mx1.freebsd.org (Postfix) with ESMTP id 1024B8FC14 for ; Mon, 28 Mar 2011 02:42:34 +0000 (UTC) Received: from sasl.smtp.pobox.com (unknown [127.0.0.1]) by a-pb-sasl-sd.pobox.com (Postfix) with ESMTP id 9822C5A8F for ; Sun, 27 Mar 2011 22:25:34 -0400 (EDT) DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=pobox.com; h=date:from :reply-to:to:subject:message-id:mime-version:content-type; s= sasl; bh=75VLiMO4MAc/UeN3+5jQ2CEwt3g=; b=OcVycoekP10Ff5WI8iqWx1+ m+Ob07bi2KhJZtgOrEWy4LPOAsDdhy7vityZLssJGkLVgTjjJHHzv2mYIntrlXU3 bX++X7iJpQg/tf76rLjP2L3lowA38JNLKlr2LwLB+OC3b/XY4z8hVXaQi6BFVbB2 VizgH/zHQ46iOr5P42qA= DomainKey-Signature: a=rsa-sha1; c=nofws; d=pobox.com; h=date:from :reply-to:to:subject:message-id:mime-version:content-type; q= dns; s=sasl; b=RPCdTUwqw6g6oPQ/uxmAmEOIiB7ynM3sy3v4dc32zMlGYCgY9 9KSJjox665yahiT9DSsqrM/YyHJNLmNAUPL/73d48OFFIgH4uCUUWKXc8+nvvKcC dicT8GKgS7NUGqvenH6Qnj8jIJ7QsLditjpwp+uKetd7yRgRKVar2KbcHE= Received: from a-pb-sasl-sd.pobox.com (unknown [127.0.0.1]) by a-pb-sasl-sd.pobox.com (Postfix) with ESMTP id 749CE5A8D for ; Sun, 27 Mar 2011 22:25:33 -0400 (EDT) Received: from [192.168.10.100] (unknown [50.35.181.63]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by a-pb-sasl-sd.pobox.com (Postfix) with ESMTPSA id F3C8A5A8C for ; Sun, 27 Mar 2011 22:25:32 -0400 (EDT) Date: Sun, 27 Mar 2011 19:23:41 -0700 (PDT) From: Luke Dean X-X-Sender: lukas@tower.lukas.is-a-geek.org To: freebsd-questions@freebsd.org Message-ID: User-Agent: Alpine 2.00 (BSF 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; format=flowed; charset=US-ASCII X-Pobox-Relay-ID: A87EE04E-58E2-11E0-95FC-E8AB60295C12-96347044!a-pb-sasl-sd.pobox.com Subject: kern.geom.journal.stats.low_mem refers to what? X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: Luke Dean List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 28 Mar 2011 02:42:35 -0000 I've recently set up gjournal on top of gmirror on FreeBSD 8.2. I understand that this setup has a lot of redundant writing. It is working, but I'm not sure I've set it up as efficiently as I should. During prolonged writes, such as copying large files to the file system across the network or producing very large logfiles, the "low_mem" and "skipped_bytes" statisics rise rapidly and the system becomes less responsive. "top" always reports free memory, so I don't think that's the issue. "journal_full" and "wait_for_copy" have never occurred. Here's a sample of what happens after a couple hours of intense writing... kern.geom.journal.stats.low_mem: 5379 kern.geom.journal.stats.journal_full: 0 kern.geom.journal.stats.wait_for_copy: 0 kern.geom.journal.stats.switches: 7543 kern.geom.journal.stats.combined_ios: 265318 kern.geom.journal.stats.skipped_bytes: 935712768 "low_mem" sounds like a bad thing. What could I do to remedy that? Did I make the journal too small? The stats say that "journal_full" has never happened, so maybe not? Is there a setting I should tweak? The Handbook says 1GB is good enough most of the time, but it also says that 3x the amount of physical memory is a good size as well. I compromised between the two and made an 8GB journal for this system that has ~4GB of memory.