From owner-freebsd-questions@FreeBSD.ORG Thu May 30 15:06:08 2013 Return-Path: Delivered-To: freebsd-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 DDC0BD9F for ; Thu, 30 May 2013 15:06:08 +0000 (UTC) (envelope-from rwmaillists@googlemail.com) Received: from mail-wg0-x22d.google.com (mail-wg0-x22d.google.com [IPv6:2a00:1450:400c:c00::22d]) by mx1.freebsd.org (Postfix) with ESMTP id 76EBCAF2 for ; Thu, 30 May 2013 15:06:08 +0000 (UTC) Received: by mail-wg0-f45.google.com with SMTP id n12so341297wgh.12 for ; Thu, 30 May 2013 08:06:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=googlemail.com; s=20120113; h=date:from:to:subject:message-id:in-reply-to:references:x-mailer :mime-version:content-type:content-transfer-encoding; bh=JXpHHB+803kgplmG8fwFnYMofcd5ACEUoRN31dMY3Jo=; b=j/yhqm0EA+0oAupp0xgl+rLw9hZMMiWJ26T5RoY/HNjfrlnpGbOVrmOL2VKm43/Rj8 +N9/3dfVVHM+csB+jCtO8WuZAdUIxd9e0ycuBTPR525Jm4xINCtdGwtX0omdgoVlwd7x j9jPOuRiSvfsD6oRo+zOtdgHkdGVCy/ciVvr00mYPrnsGD2yq9PYGsu5Vj9MWupOK93f CznHrYjMm+STiTysQ4x+0QciwHLQqtsa+7uow5tCD2+q5V1T2pKHLQ8ccscOAFJkibNk 4bnwEQ7txUWPXgG0CySEixu8ZmXrM6VGCRRJCvHMW9pR7c6JWKQ76SF6twlKGHac7CCs cEFQ== X-Received: by 10.180.184.83 with SMTP id es19mr18960400wic.54.1369926367660; Thu, 30 May 2013 08:06:07 -0700 (PDT) Received: from gumby.homeunix.com (87-194-105-247.bethere.co.uk. [87.194.105.247]) by mx.google.com with ESMTPSA id fu14sm38648600wic.0.2013.05.30.08.05.57 for (version=SSLv3 cipher=RC4-SHA bits=128/128); Thu, 30 May 2013 08:05:57 -0700 (PDT) Date: Thu, 30 May 2013 16:05:55 +0100 From: RW To: freebsd-questions@freebsd.org Subject: Re: "swap" partition leads to instability? Message-ID: <20130530160555.3104ced6@gumby.homeunix.com> In-Reply-To: References: <1369558712.96152.YahooMailNeo@web165006.mail.bf1.yahoo.com> <20130529133516.295084a6@gumby.homeunix.com> X-Mailer: Claws Mail 3.9.0 (GTK+ 2.24.17; amd64-portbld-freebsd10.0) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit 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: Thu, 30 May 2013 15:06:08 -0000 On Wed, 29 May 2013 19:52:02 +0000 (UTC) jb wrote: > RW googlemail.com> writes: > > > > > BTW you mean paging, or swap use, rather that swapping. Linux > > supports only paging, so it can be taken as read that swapping > > means paging, but FreeBSD supports both. > > Yes, there is some confusion about the diff, if any, between paging > and swapping. > > Paging - copying or moving pages between physical memory (RAM) and > secondary storage (e.g. hard disk), in both directions. > Swapping - nowdays is synonymous with "paging". > But its history is as follows (per Wikipedia): This is a bit Linux-centric. > You say that FB supports both, Linux supports paging only. > Well, Linux utilizes swap space as part of virtual memory. > So, can you elaborate more on that - what is the essence of the diff, > why should I avoid the term "swapping" when referring to Linux, > assuming VMM systems on both ? You page-out pages and swap-out processes. When FreeBSD is very short of memory it swaps-out entire processes to concentrate the memory in the running processes. Linux goes directly from paging to killing processes. You can also set vm.swap_idle_enabled to allow idle processes to be swapped during normal use. This may help if a server has a lot memory tied up in processes that tend to be idle for long periods of time - traditionally used on shell servers. These days you'd probably want to be adding more memory.