Hi All -
I'm running Apache, mod_perl and HTML::Mason on Solaris 2.6, and using
Apache::Session::File for session management. I've been monitoring free
memory as reported by top, and I'm seeing some behavior that is totally
baffling me. (If you're interested, there's a graph at:
http://www.furph.com/graph.png) Here's the scenario:
Around 6 AM, when things are relatively quiet, the graph shows about 1.3GB
free memory (out of 4GB total). As traffic picks up during the course of
the day, free memory drops to about 300MB by 3 or 4 PM. So far so good,
no big surprise - there's a lot more httpd processes running so you'd
expect more memory in use.
Odd thing #1: As it gets into evening time, load on the machine drops off
and there are fewer httpd children running, but I am not seeing free
memory return to that 1.3GB level. At most it comes back up to 400MB or
so. I don't think the httpd children are hanging on to memory, because
they cycle through pretty quickly - MaxRequestsPerChild is set to 512 and
none of the processes are ever more than a couple minutes old when I look
in. Is there any reason to think the parent httpd process would hang on
to anything?
Odd thing #2: (This part seems most bizarre to me.) At 5:15 AM, we run a
Perl script that finds and deletes Apache::Session::File session and lock
files that are older than 28 days. Usually there are about 50,000 old
files that get deleted out of about 2,300,000 total. Almost immediately,
free memory on the machine jumps back up to 1.3GB. What's up with that?
If I run the script during the middle of the day, when things are busier,
I still see the free memory jump up although not all the way to 1.3GB -
maybe to 800MB or so. Because of the rate the httpd children cycle, I
don't think it's possible any of them could be holding open filehandles to
session files that haven't changed for 28 days.
Is there something weird about the way top reports free memory? The
numbers I get seem consistent with the "free" column from vmstat. Why
would deleting a bunch of files free up 1GB of memory? Any ideas or
explanations would be much appreciated!
Thanks!
Larry Leszczynski
[EMAIL PROTECTED]
