William LeFebvre wrote:
Artem Kuchin wrote:
Hello!
Maybe someone with deeper knowledge of the internals of FreeBSD
can clean up something for me (any for many others)^
Here are lines from my top:
PID USERNAME THR PRI NICE SIZE RES STATE C TIME WCPU
COMMAND 9258 hordelo_ru 1 4 0 40992K 4260K accept 0 0:00
0.00% httpd 9257 hordelo_ru 1 44 0 40992K 4296K select 1
0:00 0.00% httpd 9259 hordelo_ru 1 4 0 40992K 4292K select
1 0:00 0.00% httpd
As you see, 'size' is the same for all processes, while RES varies.
As i understand, the real memory taken by a process is RES and SIZE
include a bunch of shares .so libs, so, if more httpd's started each
will take only about 4300K more, so, 100 https will take 430000K to
run, right?
Another question is that is httpd uses threads (as provided by
FreeBSD) starting a new thread will or will not copy executable copy
and data? Basically,
will a new thread eat another 4300K or just a little bit for its
data?
SIZE is the total amount of virtual memory that a process has
allocated. This includes text, data, and stack. It also includes
all the stuff that's shared with other processes (mostly through the
use of shared libraries).
RES is the amount of physical memory in use by the process and will
only include that part of a process's virtual memory space which is
currently allocated in physical memory.
Unfortunately, freebsd does not appear to track the amount of shared
virtual memory for each process. It could be obtained by walking
through all the pages in a process's vm map, but that would really
slow top down. I don't know of any freebsd utility that would give
that information for an individual process. But hey, if it's out
there somewhere where it is easy to grab, I would be very happy to
add it to top.
My knowledge of VM system of FReebSD is so low, that even though
i can write in C i don't know where to start here. I haven't found
anything ready for this. make search in port on 'memory' and 'ram'
does not return much.
All this i need to calculate maximum possible number of https i can
run on a box
with certain amount of memory and select proper MPM for Apache.
Somehow, i could not find any practical info on this regarding
FreeBSD.
limits how many of them can be active at a given time. You're not
just going to be able to sit down and plug numbers in to a formula
and say "voila!". You will have to observe how httpd performs in your
particular environment to see how many page faults per second it
generates and decide for yourself the point at which X pf/s is too
much.
Of course, but i need to start with something instead of just pure guess
out of the blue.
Personally, based on my experience, I would be more concerned with the
amount of available cpu cycles than memory.
CPU is more than just enough in my case. There will a a lot https
sitting there but load, i am sure, will be low.
Swapping is simply unacceptable, so i am counting only real physical ram.
However, noone mentioned anything about threads. DO they give any memory
advantage on freebsd?
--
Regards,
Artem
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