From owner-freebsd-questions@FreeBSD.ORG Wed May 29 19:52:25 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 9D30CC11 for ; Wed, 29 May 2013 19:52:25 +0000 (UTC) (envelope-from freebsd-questions@m.gmane.org) Received: from plane.gmane.org (plane.gmane.org [80.91.229.3]) by mx1.freebsd.org (Postfix) with ESMTP id 618E239C for ; Wed, 29 May 2013 19:52:25 +0000 (UTC) Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1UhmPx-0000DW-RV for freebsd-questions@freebsd.org; Wed, 29 May 2013 21:52:24 +0200 Received: from 79-139-19-75.prenet.pl ([79.139.19.75]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Wed, 29 May 2013 21:52:17 +0200 Received: from jb.1234abcd by 79-139-19-75.prenet.pl with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Wed, 29 May 2013 21:52:17 +0200 X-Injected-Via-Gmane: http://gmane.org/ To: freebsd-questions@freebsd.org From: jb Subject: Re: "swap" partition leads to instability? Date: Wed, 29 May 2013 19:52:02 +0000 (UTC) Lines: 40 Message-ID: References: <1369558712.96152.YahooMailNeo@web165006.mail.bf1.yahoo.com> <20130529133516.295084a6@gumby.homeunix.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Complaints-To: usenet@ger.gmane.org X-Gmane-NNTP-Posting-Host: sea.gmane.org User-Agent: Loom/3.14 (http://gmane.org/) X-Loom-IP: 79.139.19.75 (Mozilla/5.0 (X11; Linux i686; rv:21.0) Gecko/20100101 Firefox/21.0) 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: Wed, 29 May 2013 19:52:25 -0000 RW googlemail.com> writes: > > On Sun, 26 May 2013 12:36:42 +0000 (UTC) > jb wrote: > > > But, swapping is also a symptom, not a problem. > > It is never a good idea to let it get to that point. > > No, there are thing that are better on disk than in memory. The most > common example is tmpfs. It's much better that files left on tmpfs can > sent to disk rather tying up physical memory indefinitely. > > 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): Historically, swapping referred to moving from/to secondary storage a whole program at a time, in a scheme known as roll-in/roll-out. In the 1960s, after the concept of virtual memory was introduced — in two variants, either using segments or pages — the term swapping was applied to moving, respectively, either segments or pages, between memory and disk. Today with the virtual memory mostly based on pages, not segments, swapping became a fairly close synonym of paging. 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 ? jb