I’m using the utility osinfo to try to work out why a machine runs out of
resources from time to time. I’m a bit confused about the free memory
fields. There is a subfield that gives the free memory for Proc. On some
machines (those with 32M RAM) this value is somewhere between 4000 and 9000.
However, on a 64M machine this field is listed as zero (in both the
currently available and the low water point). This machine is also one that
never gives a moments trouble.
So can anyone explain what exactly this Proc free memory field measures?
(The troublesome machine started off with about 4000 as the Proc free
memory, and this fell to around 200 sometime before the machine got a power
cut reboot. I’m trying to understand if this falling to 200 is the sign of
something bad, or not…)
thanks
Julian Thornhill
Julian Thornhill <jth@ion.le.ac.uk> wrote:
I’m using the utility osinfo to try to work out why a machine runs out of
resources from time to time. I’m a bit confused about the free memory
fields. There is a subfield that gives the free memory for Proc. On some
machines (those with 32M RAM) this value is somewhere between 4000 and 9000.
However, on a 64M machine this field is listed as zero (in both the
currently available and the low water point). This machine is also one that
never gives a moments trouble.
So can anyone explain what exactly this Proc free memory field measures?
(The troublesome machine started off with about 4000 as the Proc free
memory, and this fell to around 200 sometime before the machine got a power
cut reboot. I’m trying to understand if this falling to 200 is the sign of
something bad, or not…)
What version of QNX are you running? In particular what version of Proc?
If this is displaying what I think its displaying, at one point it was
a meaningful value, and its dropping/running out was bad. (IIRC, That
would be in the pre-4.23 days.) After that point (4.23 and later) that
value is, essentially, meaningless.
(In pre-4.23, Proc was 16-bit code, and certain data areas were limitted
to the size of a 64k segment; this “free” memory was how much space was
left in the pre-allocated chunk, which could never exceed 64k. In 4.23
and beyond, my understanding is that the same set of tables could be
grown on demand, and, they were allocated in chunks, and the “free”
memory was how much had been allocated but not yet used up – but if
there was free system RAM when this ran to zero, it would just allocate
more rather than running out – which is why I say it is essentially
meaningless.)
-David
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