[PLUG] some additional information

wes plug at the-wes.com
Thu Mar 29 17:40:48 UTC 2012


>
>
> {If it doesn't go up then it's just normal disk caching using
> otherwise unused memory. If it
> does go up then there may be a problem.}
>
> Unfortunately grabbing almost all the system memory just to do a disk
> cache for copying a 24 gig file has just about left the system
> useless.
>

this is not how the cache is supposed to work - the memory is not reserved
for the cache, it is just used until something else needs it. it is then
immediately freed for the new use, and allocated to that. ls or vim or
anything else will never notice a lack of available memory if it is taken
by disk cache.


>
> Should not the command at least leave about 1 gig of memory alone?  I
> do confess to having a 16 processor system.
>
>
in linux, individual applications (including cp) do not have a sense of how
much memory they have used or is remaining available on the system. this is
handled by the OS. they just request the memory they need until a request
is denied (or its need is completed). how the application handles the
denial is up to the app - it could crash, or it could work with what it
has, and then re-use what it has allocated. this ecosystem of handling
needs works pretty well overall.

-wes



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