Re: [MooseFS-Users] mfsmaster memory usage

[Tom I. H. <ti...@ha...>]

"Wilson, Steven M" <st...@pu...> writes:

> On the "Info" page of the CGI display the first two lines under
> "Memory usage detailed info" are "used" and "allocated".  Looking at
> our server that peaked at a little over 200 million files and is now
> down to about 140 million files, I see 42GiB being used but 68GiB
> allocated.

Ah, so they're reusing data structures instead of freeing them up and
reallocating them.  An efficiency thing, maybe?  In any case, whether
it's the application or the malloc arena holding the unused memory
doesn't really make a difference to the virtual size of the heap.

I'm assuming that the added complexity in the application isn't making
it leak memory, of course.  :)

> Using top, it looks like resident memory is almost equal to the amount
> of virtual memory for the mfsmaster process indicating that the memory
> is not only allocated but also occupying physical memory.

That's not any worry unless the physical memory is being kept from being
used for something else that needs it.  If the mfsmaster is repeatedly
touching memory that it's not really using, thus keeping it from being
paged out, while another application needs more, that would be silly.
If it's just leaving it sitting there until it can use it again, there's
no worry.

So in your situation, the natural thing to do would be to make sure that
the mfsmaster has enough physical memory to handle the peak need, and
not make it run any other application that competes with it for the RAM.

-tih
-- 
Elections cannot be allowed to change anything.  --Dr. Wolfgang Schäuble