Re: top(1) and the meaning of columns

[Mike McCarty <Mike.McCarty@sbcglobal.net>]

Tshepang Lekhonkhobe wrote:

> What does thrashing mean?

Literally, "thrashing" means beating repetedly. In this context it
is being used figuratively. There are two possible meanings in
this regard. One of them is when disc is being cached in faster
memory (these days, RAM), but the algorithm for caching is not working
well in selecting what parts to try to retain in memory, resulting
in more disc accesses than would be required were caching not being
used. The other meaning is when disc is being used for virtual memory,
but the algorithm is not working well, resulting in a high proportion
of accesses being cache misses, resulting in many disc accesses.

In either case, this results in the system being very slow.

It is provable that no single algorithm works for either case.
IOW, for any given algorithm, there is a circumstance in which
using the memory/disc copies are worse than not using them.

Mike
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