Date: Wed, 29 May 2013 19:52:02 +0000 (UTC) From: jb <jb.1234abcd@gmail.com> To: freebsd-questions@freebsd.org Subject: Re: "swap" partition leads to instability? Message-ID: <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>
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RW <rwmaillists <at> 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
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