Am I short of memory for the JVMs ?
in [Java Help]
|
Prev: Is this GC.log summary indicating memory leak ?
Next: Can I install new JavaRuntime version on top of previous? Automatic (CLASS)PATH change?
From: Krist on 18 Feb 2010 02:59 Hi all, In our apps server, we are running 4 JVMs with the following settings : JVM_1 : -ms3072M -mx3072M -XX:MaxPermSize=1024M JVM_2 : -ms3072M -mx3072M -XX:MaxPermSize=1024M JVM_3 : -ms1024M -mx1536M -XX:MaxPermSize=1024M JVM_4 : -ms128M -mx128M -XX:MaxPermSize=128M We are running on 12 GB memory and 2 CPU Xeon dualcore and Redhat 4. During peak load, when I type free -m command from Linux , the output is : Mem total : 12010 used : 11988 free : 21 Swap total : 4096 used : 0 free : 4096 ( no matter how long, the swap is never used by the system ) Based on this , am I running short of memory ? Thank you, xtanto
From: Martin Gregorie on 18 Feb 2010 09:25 On Wed, 17 Feb 2010 23:59:38 -0800, Krist wrote: > Hi all, > > In our apps server, we are running 4 JVMs with the following settings : > > JVM_1 : -ms3072M -mx3072M -XX:MaxPermSize=1024M JVM_2 : -ms3072M > -mx3072M -XX:MaxPermSize=1024M JVM_3 : -ms1024M -mx1536M > -XX:MaxPermSize=1024M JVM_4 : -ms128M -mx128M -XX:MaxPermSize=128M > > We are running on 12 GB memory and 2 CPU Xeon dualcore and Redhat 4. > > During peak load, when I type free -m command from Linux , the output is > : > > Mem total : 12010 used : 11988 free : 21 Swap total : 4096 > used : 0 free : 4096 ( no matter how long, the swap is never > used by the system ) > > Based on this , am I running short of memory ? > Its not swapping, so its probably happy. The only thing I notice is that there's only 21 MB left for disk buffering, etc. Are you noticing slow I/O or reduced network throughput? Have you used sar or other monitoring tools to examine system operation? -- martin@ | Martin Gregorie gregorie. | Essex, UK org |
From: Thomas Pornin on 18 Feb 2010 09:57 According to Martin Gregorie <martin(a)address-in-sig.invalid>: > > During peak load, when I type free -m command from Linux , the output is > > : > > > > Mem total : 12010 used : 11988 free : 21 Swap total : 4096 > > used : 0 free : 4096 ( no matter how long, the swap is never > > used by the system ) > > > > Based on this , am I running short of memory ? > > > Its not swapping, so its probably happy. > > The only thing I notice is that there's only 21 MB left for disk > buffering, etc. This output of 'free -m' is incomplete. It should look like this: total used free shared buffers cached Mem: 7937 1916 6021 0 197 849 -/+ buffers/cache: 869 7068 Swap: 30513 0 30513 Note that there are _two_ 'free' numbers for RAM (not counting swap). On the first line, this is the totally unused RAM. On the second line, this is the sum of that unused RAM and the RAM currently used to cache disk data. Here, my PC is rather freshly rebooted so there are 6 GB untouched, but already 1 GB used for disk cache. RAM used as a disk cache can be freed immediately, so it is "kind-of-free". The amount of unused RAM should gradually lower, down to a small proportion of the total RAM, while the computer is up (it does not reach zero because the kernel keeps a bit of unused RAM for some emergency cases deep within the kernel itself). I guess that the '21' above is the amount of unused RAM, and it is not a concern. --Thomas Pornin
From: Krist on 20 Feb 2010 01:23 On 18 Feb, 21:57, Thomas Pornin <por...(a)bolet.org> wrote: > According to Martin Gregorie <mar...(a)address-in-sig.invalid>: > > > > During peak load, when I type free -m command from Linux , the output is > > > : > > > > Mem total : 12010 used : 11988 free : 21 Swap total : 4096 > > > used : 0 free : 4096 ( no matter how long, the swap is never > > > used by the system ) > > > > Based on this , am I running short of memory ? > > > Its not swapping, so its probably happy. > > > The only thing I notice is that there's only 21 MB left for disk > > buffering, etc. > > This output of 'free -m' is incomplete. It should look like this: > > total used free shared buffers cached > Mem: 7937 1916 6021 0 197 849 > -/+ buffers/cache: 869 7068 > Swap: 30513 0 30513 > > Note that there are _two_ 'free' numbers for RAM (not counting swap). On > the first line, this is the totally unused RAM. On the second line, this > is the sum of that unused RAM and the RAM currently used to cache disk > data. Here, my PC is rather freshly rebooted so there are 6 GB > untouched, but already 1 GB used for disk cache. RAM used as a disk > cache can be freed immediately, so it is "kind-of-free". > > The amount of unused RAM should gradually lower, down to a small > proportion of the total RAM, while the computer is up (it does not reach > zero because the kernel keeps a bit of unused RAM for some emergency > cases deep within the kernel itself). I guess that the '21' above is the > amount of unused RAM, and it is not a concern. > > --Thomas Pornin Hi Thomas, Thanks for your reply. The complete output is like this : total used free shared buffers cached Mem: 12010 11980 30 0 149 2326 -/+ buffers/cache: 9504 2505 Swap: 4095 0 4095 Does it mean actually there is still 2505+30 kb Free = 2.5 GB ?? Thank you, Krist
From: Thomas Pornin on 20 Feb 2010 08:53
According to Krist <krislioe(a)gmail.com>: > Does it mean actually there is still 2505+30 kb Free = 2.5 GB ?? Basically, yes. No worry there. --Thomas Pornin |