Hi Mark, On Sun, Sep 9, 2012 at 12:50 PM, Mark Phillips wrote: > I have been having some issues with an old server running a jsp > applicaition (tomcat web server and java 1.5....I said it was old!). I > looked at the partitions and found: > > Last login: Sun Sep 9 11:57:49 2012 from 192.168.25.150 > mark@gandalf:~$ df -h > Filesystem Size Used Avail Use% Mounted on > /dev/hda6 110G 61G 44G 58% / > tmpfs 63M 0 63M 0% /dev/shm > /dev/hda1 30M 7.3M 21M 27% /boot > mark@gandalf:~$ > > tmpfs or /dev/shm is at 0%. Usually, a zero anywhere is bad thing....;) so > should I do something about this? > > This is 63M with 0 used above. You can expand it for better performance, but I doubt that your utilization issues are /dev/shm kernel intermessage processing related. In a J2EE system, it would be memory, garbage collection, or a kernel based known memory error. But if you are running Ultramonkey or a databasae, you could use all of /dev/shm during heavy network use, so you can easily expand /dev/shm (see below). Reference: http://www.cyberciti.biz/tips/what-is-devshm-and-its-practical-usage.html > I goolged /dev/shm and understand that it is a ram disk for interprocess > communications. Wonderful. Should I be worried it is at 0% Should I > increase the size? Running top shows these resources in the system" > > Tasks: 60 total, 1 running, 59 sleeping, 0 stopped, 0 zombie > Cpu(s): 1.0% us, 0.3% sy, 0.0% ni, 98.4% id, 0.0% wa, 0.3% hi, 0.0% si > Mem: 127152k total, 124740k used, 2412k free, 6896k buffers > Swap: 489940k total, 0k used, 489940k free, 45500k cached > > > If I should increase the size of /dev/shm, would I edit fstab and add this > line > > none /dev/shm tmpfs defaults,size=8G 0 0 > > and then > > mount -o remount /dev/shm > > You can use /dev/shm to improve the performance of applicationsoftware such as Oracle or overall Linux system performance. On heavily loaded system, it can make tons of difference. For example VMware workstation/server can be optimized to improve your Linux host's performance (i.e. improve the performance of your virtual machines). In this example, remount /dev/shm with 8G size as follows: # mount -o remount,size=8G /dev/shm To be frank, if you have more than 2GB RAM + multiple Virtual machines, this hack always improves performance. In this example, you will give you tmpfs instance on /disk2/tmpfs which can allocate 5GB RAM/SWAP in 5K inodes and it is only accessible by root: # mount -t tmpfs -o size=5G,nr_inodes=5k,mode=700 tmpfs /disk2/tmpfs Where, - *-o opt1,opt2 * : Pass various options with a -o flag followed by a comma separated string of options. In this examples, I used the following options: - *remount* : Attempt to remount an already-mounted filesystem. In this example, remount the system and increase its size. - *size=8G or size=5G* : Override default maximum size of the /dev/shm filesystem. he size is given in bytes, and rounded up to entire pages. The default is half of the memory. The size parameter also accepts a suffix % to limit this tmpfs instance to that percentage of your pysical RAM: the default, when neither size nor nr_blocks is specified, is size=50%. In this example it is set to 8GiB or 5GiB. The tmpfs mount options for sizing ( size, nr_blocks, and nr_inodes) accept a suffix k, m or g for Ki, Mi, Gi (binary kilo, mega and giga) and can be changed on remount. - *nr_inodes=5k* : The maximum number of inodes for this instance. The default is half of the number of your physical RAM pages, or (on a machine with highmem) the number of lowmem RAM pages, whichever is the lower. - *mode=700* : Set initial permissions of the root directory. - *tmpfs* : Tmpfs is a file system which keeps all files in virtual memory. *How do I restrict or modify size of /dev/shm permanently?* You need to add or modify entry in /etc/fstab file so that system can read it after the reboot. Edit, /etc/fstab as a root user, enter: # vi /etc/fstab Append or modify /dev/shm entry as follows to set size to 8G none /dev/shm tmpfs defaults,size=8G 0 0 Save and close the file. For the changes to take effect immediately remount /dev/shm: # mount -o remount /dev/shm > Thanks, > > > Mark > > P.S. The issues I am having with the application may have nothing to do > with this situation...could be some bad programming....ie a bug. > > P.P.S. I am running Linux version 2.6.8-2-386 ( > horms@tabatha.lab.ultramonkey.org) (gcc version 3.3.5 (Debian > 1:3.3.5-13)) (yes, I said it was old....) Consider it my contribution to > keeping old hardware out of the dump! > > > > --------------------------------------------------- > PLUG-discuss mailing list - PLUG-discuss@lists.plug.phoenix.az.us > To subscribe, unsubscribe, or to change your mail settings: > http://lists.PLUG.phoenix.az.us/mailman/listinfo/plug-discuss > -- (503) 754-4452 Android (623) 239-3392 Skype (623) 688-3392 Google Voice ** it-clowns.com Chief Clown