David Scheidt wrote:
On Sat, Jan 17, 2009 at 01:25:19AM +0000, RW wrote:
On Fri, 16 Jan 2009 22:23:06 +0100 (CET)
Wojciech Puchar <woj...@wojtek.tensor.gdynia.pl> wrote:
When I boot this machine it usually shows (in top) about 11 G Free
in the Mem: line
The machine, in this snippet, has been up for 5 days 22 hours and
change and it now shows 1436M free in the Mem: line
I've been watching the number and it has been slowly decreasing
over the 5 days since its last boot. It looks like as the Free
line trends down, the Inact value trends up to keep the total Mem
used at the installed 12G
ALL unused memory is used as disk cache in FreeBSD.
Although, looking at the output of top, most of the memory is in the
inactive state. As I understand it cache pages go from active to
cached, and the inactive queue contains pages that need to be written
out to swap before they can be reused.
No. It just means they're not active -- nothing has touched them
"recently". They may be dirty. They may not be. Recently means the
last 20 seconds to a minute, depending.
The very high level of inactive memory looks suspiciously like a
memory-leak to me. Hopefully someone who knows more about this will
step in - don't take my word for it.
I have no data on the system in question, but it's very common for a
machine to have large amounts of inactive memory, particularly one
that's not under any sort of memory pressure.
My basically idle workstation has 1.5 GB of memory, 5 MB free, and over
a gig inactive. Since I'm not doing anything with it (I'm writing this
from another machine), and its just hanging out, this is what I'd expect.
Should it do something that requires memory, the pager will toss clean
inactive pages to the free list, and they'll be reused. Of course, if
what they're required for is something they already have in them (like
the code segments of "recently" terminated application that's
restarted), they'll get reused, saving having to read them from disk.
The only time you'll large amounts of memory on the Free list is when
a machine is first booted and hasn't touched that memory for anything,
or when an application that's got a large dyanmically allocated block
of memory terminates. The rest of the time, the free list should be
small.
If the machine isn't swapping, there's usually nothing to worry about.
For comparison's sake here is the top -P output from my Dell 2950 dual
quad core server; this one is has 8 GB or RAM installed
last pid: 94403; load averages: 0.02, 0.38, 0.63 up 11+21:13:56
12:12:47
69 processes: 1 running, 68 sleeping
CPU 0: 0.0% user, 0.0% nice, 0.0% system, 0.0% interrupt, 100% idle
CPU 1: 0.0% user, 0.0% nice, 0.0% system, 0.0% interrupt, 100% idle
CPU 2: 0.0% user, 0.0% nice, 0.0% system, 0.0% interrupt, 100% idle
CPU 3: 0.0% user, 0.0% nice, 0.0% system, 0.0% interrupt, 100% idle
CPU 4: 0.0% user, 0.0% nice, 0.0% system, 0.0% interrupt, 100% idle
CPU 5: 0.0% user, 0.0% nice, 0.0% system, 0.0% interrupt, 100% idle
CPU 6: 0.0% user, 0.0% nice, 0.0% system, 0.0% interrupt, 100% idle
CPU 7: 0.0% user, 0.0% nice, 0.0% system, 0.0% interrupt, 100% idle
Mem: 226M Active, 2683M Inact, 465M Wired, 552K Cache, 214M Buf, 4537M Free
Swap: 16G Total, 16G Free
> uname -a
FreeBSD dl 7.1-STABLE FreeBSD 7.1-STABLE #7: Mon Jan 5 13:53:52 EST
2009 r...@dl:/usr/obj/usr/src/sys/AMD amd64
And here is the top -P from my Dell 2850 dual core server with 12 GB RAM
installed:
last pid: 9877; load averages: 0.07, 0.04, 0.07 up 6+22:31:45
12:20:13
98 processes: 1 running, 97 sleeping
CPU 0: 0.0% user, 0.0% nice, 0.0% system, 0.0% interrupt, 100% idle
CPU 1: 0.0% user, 0.0% nice, 1.5% system, 0.0% interrupt, 98.5% idle
CPU 2: 0.4% user, 0.0% nice, 0.0% system, 0.0% interrupt, 99.6% idle
CPU 3: 0.0% user, 0.0% nice, 0.0% system, 0.0% interrupt, 100% idle
Mem: 242M Active, 10G Inact, 431M Wired, 128M Cache, 214M Buf, 943M Free
Swap: 2014M Total, 2014M Free
FreeBSD www 7.1-STABLE FreeBSD 7.1-STABLE #2: Tue Jan 6 19:24:57 EST
2009 r...@www:/usr/obj/usr/src/sys/DELL64 amd64
Both of these machines are running nearly identical software; the main
difference is that the 2950 quad core is also running Samba. I can see
the numbers move up and down between Free and Inactive on the 2950, but
the 2850 just continues to have Free in decline; it now shows 10G
inactive. When I stop and restart apache, MySQL and Mailman on the
2850, I can see an small increase in the Free and a decrease in
inactive. As far as I know, neither machine has ever gone into swap.
The 2850 has only 2 G of swap space because originally the machine only
had 1 G of RAM. I don't know what the Free vs Inactive numbers were on
that box back then. I just never noticed the numbers.
Again, I don't know that there is any problem at all, I'm just trying to
understand why the 2 machines would have such different amounts of
Inactive and Free memory.
Tim
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