Re: Possible to turn off file system cache?

Allen Kirby wrote:
>
> Dan Bikle wrote:
> <snip>
> > This is a huge memory size for a process. I can only make sense
> > of it if I conclude that ps is adding shared memory to private
> > memory in the display but that the process is not really 223584 kb.
> > If I want to find the true size of the process I need to subtract
> > 216062460 bytes from 223584 kb to come up with 12586 kb. This is
> > still a large size for a process but we are talking about an Oracle
> > process (Oracle software has a rep for being a resource hog).
Try using /usr/ucb/ps -augx and look at the RSS field. thats the real RAM used, look at the man page for it too.

On the shared memory thing, allen is correct, each process doesnt make a copy, they share the same copy. This is the same way that dynamic shared objs ( libs) work. The mapper will just map a region of the processes address space to the common load of the shared object.
In truth, for each shared region there is usually a small private region that each process needs to copy. An example is libc, its global vars like errno, each process has a local copy.

try doing:
/usr/proc/bin/pmap PID
to examine the regions of memory a process is using. Note if the HEAP section grows over time. (usually indicated a mem leak )

>
> Daniel,
> Process size is very tricky. It does not (to the best of my knowledge)
> include
> any shared memory segments (correct me if I'm wrong here). It
> definitely does
> not COPY shared memory for each process. That totally defeats the
> purpose.
> Shared memory is simply attached to the processes memory as a pointer.
 

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