memory usage question

[jujae yun]

1. current system config
- HP rp3440
- memory : 1G
- OS Version(HP UNIX 11.23)

2. TOP memory result
- Memory : 304,884K (161,584K) real,
536,222K (356,332K) virtual,
199,536K free

3. Glance memory result
- Mem Util Current : 81% Avg : 81% High : 81%
Swap Util Current : 4% Avg : 4% High : 4%

- Total VM:523mb, Sys Mem:319mb, User Mem:305mb, Phys Mem:1022mb Active VM:284mb Buf Cache:204mb, Free Mem:192mb, FileCache : na

4. Dmesg memory result
- Memory Information
Physical page size=4,096bytes, logical page size=4,096bytes
physical : 1,046,528 Kbytes, lockable : 675,692Kbytes, available : 747,260Kbyes


※ Question
1) current OS only operation:
Glance Tool result : memory usage 81% , Free Memory 19%.
Is this correct that glance tools display memory usage 81% ?

2) if 81% are correct, can free memory extend without add memory ??

[Rita C Workman]

Your only running your O/S on this box and your at 81% utilization.

Couple thoughts:

11.23 and 1Gb of memory. That's kind of slim to me. You might want to consider at least 4Gb.

How your parms are set, can affect how much for overhead the O/S is taking. But you don't mention how your parms are set. If you left them at default values, that could be why you see this. dbc_max% at 50% is one most folks change immediately; hence dbc_min% should also be adjusted.

Just my thoughts...

[Don Morris_1]

1) Well, let us walk the math.

Mem Util is physical memory. Glance shows 319Mb (System), 305Mb (User) and 204Mb in the Buffer Cache (DBC tunables control the sizing).

319Mb + 305Mb + 204Mb = 828Mb.

Total Physical Memory is 1022Mb.

(828 / 1022) * 100 = 81.01761252%

Yes, 81% is reasonably correct (you can't blame Glance for a little rounding).

And by the way -- that entirely agrees with top since top reports User only. (So top says 304,884K and Glance says 305Mb... close enough... 536,222K virtual in top... 523Mb in Glance...)

2) I have no idea what you mean by "can free memory extend without add memory". If you add memory (and since this is 11.23, that means you're talking about rebooting the system), certainly there will be more memory in total -- and assuming the same workload and since DBC isn't eating too much Free memory now, yes there will likely be more of that memory free.

If you don't add memory -- and you want to increase the Free Memory on the system, you'll need to lower the DBC tunables or decrease the system workload (see prior message in thread). Keep in mind that you have 19% of the system free now -- so the system is in a reasonable state of equilibrium. This is important because it means that the kernel is not going to be at all aggressive about reclaiming System memory -- it prefers to leave it where it is for caching [once allocated but freed memory is assumed to be needed again if there's no other demands for it].

In other words, don't get hung up on the amount of free memory. Either you've put your workload on the box already (in which case, you've got a reasonable amount of RAM to grow still, no performance issues) -- or you have yet to do so. Obviously, if your workload is a 4Gb database that needs to be locked in RAM to work well, you'll lack memory. Only you would know. If it is more of a webserver/dynamic environment... you should really test the workload out and see what the steady state of the system becomes (when you start having User memory causing some pressure, the Dynamic part of the DBC will kick in and the Buffer Cache may shrink, or the System may give up some memory... depends on what's going on).

2.5) If you just want to reduce System Memory consumption itself (and I doubt you'll be able to by very much - 1Gb is not a lot of wiggle room for 11.23), you may want to look at some of your kernel tunables (SysV message queues and semaphores can cause large kernel allocations, etc.) Others here can likely help you more with that.

[whiteknight]

Hi yun,

1) personally i prefer glance tool memory report. It is very precise and clear.

2) Your swap space is 4% there is no sign of memory pressure.

I will say your server still fine....
1 GB for 11.23 is quite low side.. if you have budget add more memory

WK