Re: why swap at all?
From: Kyle Moffett
Date: Wed May 26 2004 - 18:33:34 EST
On May 26, 2004, at 12:58, John Bradford wrote:
A lot of people feel subjectively that swap makes a system slow.
There'sIt's true that physical RAM or swap, over and above the minimum needed
anecdotal evidence that swap does horrible things or "must be badly
because the machine gets slow" on almost every operating system that
supports swapping. In most cases, it's just a case where the real
set has exceeded physical memory, and in that case, swap is just
it's supposed to be doing.
the working set is usually beneficial. However where there is
which will never be touched during normal usage, adding swap will not
If your RAM happens to be large enough to contain not only everything
you ever want to even read *and* all the space you need for
you have nothing to gain from using swap. On the other hand, if you
grepping through a kernel source tree, the first time it is read from
disk, but after
that it is stored in cache in your RAM. If you have swap, anonymous
RAM that are not in use can be paged out while you do your grepping,
you are grepping through a 900MB+ dataset and only have 1GB RAM. Swap
allows non-filesystem-backed pages to be pushed to disk for some
backed pages to be loaded and used.
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