Date: Thu, 30 May 2013 16:05:55 +0100 From: RW <rwmaillists@googlemail.com> To: freebsd-questions@freebsd.org Subject: Re: "swap" partition leads to instability? Message-ID: <20130530160555.3104ced6@gumby.homeunix.com> In-Reply-To: <loom.20130529T213928-77@post.gmane.org> References: <1369558712.96152.YahooMailNeo@web165006.mail.bf1.yahoo.com> <loom.20130526T143506-872@post.gmane.org> <20130529133516.295084a6@gumby.homeunix.com> <loom.20130529T213928-77@post.gmane.org>
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On Wed, 29 May 2013 19:52:02 +0000 (UTC) jb wrote: > RW <rwmaillists <at> 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.
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