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+--- Thread: Reducing memory usage (/thread-10288.html)
Reducing memory usage - pete - 04-07-2010 11:27 AM
I'm using way more memory than is allocated for me by the virtual machine hosting service (limit is 512MB with 1024MB burst). I checked what is running using the top command and found that I have two large apache2 instances, each clobbering 277MB. Why two? Also, MySQL should have very little work to do but still uses 144MB.
Am I doing something wrong? Can I force these processes to be more frugal?
Note that unfortunately I can't create a swap disk or file, the VPS doesn't support that.
Following is what top tells me (sorted by memory usage):
Code:
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
13770 www-data 18 0 277m 5036 1440 S 0 0.5 0:00.19 apache2
18199 www-data 15 0 277m 4980 1436 S 0 0.5 0:00.26 apache2
22015 mysql 15 0 144m 19m 5916 S 0 1.9 0:00.57 mysqld
31755 bind 22 0 69444 10m 2076 S 0 1.1 0:00.01 named
25710 vu2000 15 0 35532 9.9m 3240 S 0 1.0 0:00.18 php5-cgi
21768 syslog 15 0 34320 1352 976 S 0 0.1 0:00.50 rsyslogd
21542 vu2001 15 0 33752 7948 2864 S 0 0.8 0:00.64 php5-cgi
21543 vu2001 15 0 33752 7948 2864 S 0 0.8 0:00.58 php5-cgi
25711 vu2000 15 0 33200 7348 2828 S 0 0.7 0:00.22 php5-cgi
5950 vu2002 18 0 31136 5852 3872 S 0 0.6 0:00.00 php5-cgi
25708 vu2000 17 0 31136 5852 3872 S 0 0.6 0:00.00 php5-cgi
21540 vu2001 16 0 31136 5848 3872 S 0 0.6 0:00.00 php5-cgi
5952 vu2002 15 0 31016 3292 1252 S 0 0.3 0:00.00 php5-cgi
5953 vu2002 16 0 31016 3292 1252 S 0 0.3 0:00.00 php5-cgi
13765 root 18 0 12944 9320 2224 S 0 0.9 0:00.13 ispcp-apache-lo
13768 root 18 0 12928 9352 2224 S 0 0.9 0:00.20 ispcp-apache-lo
23564 postgrey 18 0 11652 8416 2772 S 0 0.8 0:00.08 postgrey
29847 root 15 0 8500 2724 2152 S 0 0.3 0:00.06 sshd
11881 polw 18 0 8100 5948 1484 S 0 0.6 0:00.28 policyd-weight
15987 polw 15 0 8100 5936 1476 S 0 0.6 0:00.08 policyd-weight
22480 polw 15 0 7964 5332 1004 S 0 0.5 0:00.01 policyd-weight
22479 polw 16 0 7836 5564 1248 S 0 0.5 0:00.03 policyd-weight
13769 www-data 18 0 6284 2140 584 S 0 0.2 0:00.00 apache2
23850 root 18 0 6284 3632 2072 S 0 0.3 0:00.02 apache2
11714 postfix 15 0 5996 1852 1464 S 0 0.2 0:00.03 qmgr
13767 www-data 16 0 5964 2064 516 S 0 0.2 0:00.00 apache2
7223 postfix 15 0 5860 1736 1388 S 0 0.2 0:00.00 pickup
11711 root 15 0 5848 1788 1424 S 0 0.2 0:00.14 master
21834 root 15 0 5564 1056 648 S 0 0.1 0:00.32 sshd
13823 root 18 0 4384 1888 1448 S 0 0.2 0:00.00 bash
23583 root 15 0 2780 1324 580 S 0 0.1 0:00.10 authdaemond
21758 root 20 0 2392 556 308 T 0 0.1 0:00.00 init
1 root 15 0 2392 1336 1088 S 0 0.1 0:00.32 init
23579 root 15 0 2368 912 580 S 0 0.1 0:00.06 authdaemond
23580 root 15 0 2368 912 580 S 0 0.1 0:00.07 authdaemond
23581 root 15 0 2368 912 580 S 0 0.1 0:00.09 authdaemond
9431 root 18 0 2332 1104 876 R 0 0.1 0:00.00 top
23582 root 15 0 2148 640 344 S 0 0.1 0:00.06 authdaemond
23574 root 18 0 2144 716 560 S 0 0.1 0:00.00 authdaemond
21756 root 15 0 2084 868 680 S 0 0.1 0:00.02 cron
23595 root 15 0 1980 612 516 S 0 0.1 0:00.00 couriertcpd
23607 root 15 0 1980 612 516 S 0 0.1 0:00.05 couriertcpd
23605 root 18 0 1868 444 356 S 0 0.0 0:00.03 courierlogger
23627 root 15 0 1868 612 512 S 0 0.1 0:00.00 inetd
23573 root 25 0 1868 448 356 S 0 0.0 0:00.00 courierlogger
23594 root 18 0 1868 448 356 S 0 0.0 0:00.00 courierlogger
21750 root 21 0 1844 536 440 S 0 0.1 0:00.00 dd
13764 root 15 0 1744 480 412 S 0 0.0 0:00.00 sh
13766 root 16 0 1744 476 412 S 0 0.0 0:00.00 sh
21863 root 18 0 1744 536 444 S 0 0.1 0:00.00 mysqld_safe
22017 root 19 0 1660 536 460 S 0 0.1 0:00.00 logger
23885 root 18 0 1660 448 376 S 0 0.0 0:00.00 ispcp_daemonRE: Reducing memory usage - BeNe - 04-07-2010 03:25 PM
--> http://www.isp-control.net/documentation/doku.php?id=howto:miscellaneous:run_ispcp_on_a_low_resources_system
Greez BeNe
RE: Reducing memory usage - pete - 04-08-2010 03:11 PM
Thanks BeNe, I'll try that.
RE: Reducing memory usage - dcreation - 04-08-2010 08:58 PM
Your Apache dont use that much memory
It uses "0,5% of total" which means around 3MB.
RE: Reducing memory usage - kilburn - 04-08-2010 10:24 PM
Tracking memory usage is not a simple task, and dcreation gave you an initial hint of it.
First of all, assuming that you have no SWAP space, the virtual memory (VIRT) used by a process is completely irrelevant.
Next, the most important figure is the physical memory being used (RES column), which says that your apache instances are consuming approximately 5mb each).
Nevertheless, this is not entirely true, as part of this memory is shared with other processes (those that use the same libraries). A hint about the amount of memory that *might* be shared with other processes is shown in the SHR column. For your apache case, this column shows that approx. 1.3mb of each apache process are potentially being shared (not just among the apache process, but with any other program using the same libs).
Finally, adding the RES value of all your processes gives you a *worst case* (this is, considering that no memory is shared between processes at all which is NOT the case) of 180mb being used by your system.
RE: Reducing memory usage - pete - 04-09-2010 07:29 PM
BeNe, your suggestion worked a treat, thanks.
dcreation, in theory you're right but in my case the VPS I'm using doesn't have swap space so all virtual memory equals virtual machine memory. My limit is 1GB and my server is often dangerously close to that mark. Not surprisingly, at times things stop working due to memory allocation errors.
With BeNe's help, I now reduce overall memory down to about 400mb.
(04-08-2010 10:24 PM)kilburn Wrote: First of all, assuming that you have no SWAP space, the virtual memory (VIRT) used by a process is completely irrelevant.
Just when I thought I could understand this stuff someone throws a spanner in the works.
What is virtual memory then?
I mean, in C (and implicitly C++) we use malloc and free to manage the applications heap storage. Apart from the heap, there is stack space, code of the module itself and shared libraries, but combined, these would be a small fraction of the 144mb stated.
So I assume that a large portion of the 144mb has been allocated via [many calls to] malloc. In the absence of a swap device, where exactly would the OS put allocated memory?
I can only assume that the "no" in your comment is a typo. If I don't have a SWAP device, then surely virtual memory=physical memory (with the exceptions of shared code you mentioned), right?
If not, what is "virtual memory" in top's vocabulary?
RE: Reducing memory usage - kilburn - 04-10-2010 03:27 AM
See this thread for further insight