Christopher Cowart wrote:
I have a couple FreeBSD boxes that are providing a captive portal
wifi authentcation system. Without delving into the implementation
details, I'm running dhcpd, squid, and apache. We have in-house perl CGI
scripts that handle session and IP management, dynamically creating and
destroying netgraph nodes (ng_nat), connecting them to ipfw (ng_ipfw),
and altering the contents of access tables.
Right now, I'm seeing peaks of about 300 authenticated users; I'm
expecting this to grow about 200% when everyone gets back from summer
break. I'm trying to look at system load statistics to reassure myself
we'll be fine in a month -- or to panic and start throwing more hardware
What is the difference between the SIZE and RES fields of top? Better
yet, what does top(1) mean by "the total size of the process (text,
data, and stack)" and "the current amount of resident memory"? How does
this work with a threaded program like apache? If all the threads share
the same text and most (all?) of the same data pages, what's the best
way to figure out the fixed cost and the average per-thread cost?
Some sample top output on this host:
Mem: 131M Active, 3754M Inact, 425M Wired, 177M Cache, 214M Buf, 3422M Free
Swap: 16G Total, 24K Used, 16G Free
PID USERNAME THR PRI NICE SIZE RES STATE C TIME WCPU COMMAND
32361 root 1 96 0 106M 16604K select 2 0:02 0.00% httpd
50687 www 1 20 0 106M 17196K lockf 0 0:01 0.00% httpd
I'm having a hard time accounting for the 3.8GB of inactive memory
(which as I understand, represents physical pages that are in-use but
not recently used, prime candidates for being swapped out if the free
page count gets low). Maybe better understanding the RES verses SIZE
data along with their relation to threads will explain what's going on
One of my concerns is that a large chunk of memory is going to belong to
the kernel in my configuration. I found vmstat -m (selected output lines
| libalias 5629 3251K - 19760019 128
| ifnet 13 25K - 13 256,2048
| dummynet 22 8K - 26 256,512,1024
| netgraph_msg 0 0K - 101991 64,128,256,512,1024,4096
| netgraph_node 72 18K - 56133 256
| netgraph_hook 284 36K - 30204 128
| netgraph 283 16K - 30203 16,64,128
| netgraph_parse 0 0K - 22650 16
| netgraph_sock 0 0K - 48581 128
| netgraph_path 0 0K - 71508 16,32
Does this really mean that my netgraph nodes (and their libalias
instances) are really eating up less than 4MB of memory on the system?
The only other "big spender" appears to be devbuf at 35185K.
I also found `netstat -m':
| 1026/1599/2625 mbufs in use (current/cache/total)
| 1023/1513/2536/25600 mbuf clusters in use (current/cache/total/max)
| 1/678 mbuf+clusters out of packet secondary zone in use (current/cache)
| 0/121/121/12800 4k (page size) jumbo clusters in use (current/cache/total/max)
| 0/0/0/6400 9k jumbo clusters in use (current/cache/total/max)
| 0/0/0/3200 16k jumbo clusters in use (current/cache/total/max)
| 2302K/3909K/6212K bytes allocated to network (current/cache/total)
| 0/0/0 requests for mbufs denied (mbufs/clusters/mbuf+clusters)
| 0/0/0 requests for jumbo clusters denied (4k/9k/16k)
| 0/0/0 sfbufs in use (current/peak/max)
| 0 requests for sfbufs denied
| 0 requests for sfbufs delayed
| 60 requests for I/O initiated by sendfile
| 0 calls to protocol drain routines
Again, this looks like chump change against my top output. What category
does kernel memory get lumped into in top?
I'd appreciate any help you can offer in terms of profiling memory usage
and actually understanding what some of these figures mean.
IANAE, don't wanna presume, just wanna keep your thread alive and
see if you've read the FAQ --- Your basic questions sound real similar
to questions one and two here:
Once again, I'm hoping you can get someone to discuss your concerns
who has a better understanding of FBSD's memory reporting than I do.
AFAIK, though, there might be some reason to be concerned; Squid tends
to hog memory IME.
Surely you cant be serious."
"I am serious, and dont call me Shirley.
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