Author Topic: linux ram management,cached buffered & actually free mem (Read 4130 times)

Ricky · « **on:** January 04, 2007, 09:08:28 PM »

Somehow I never noticed this on that server.

Ok the thing is like this..

I have this remote linux server I manage from my place, its having 1GB RAM and its p4 2.6 ,120 GB SATA. Lately I directed my datacenter people to add another hdd in it and added 80GB hdd, today I was configuring it ie. partitioning , formatting and making it in use.
I noticed that top is showing that only ~240MB RAM is available, I checked and found that process runing on it hardly needs ~200MB RAM so it means around ~800MB should be available all the time, infact earlier to adding this hdd (which required reboot), it was always that around 700-800MB RAM was always free.
But now after this reboot and hdd addition only 250-350MB of RAM is free at any given time.

It just reminded that linux try to use all free RAM by doing disk cache in free RAM ie. actually RAM is free but frequently accessed data is mvoed to that free RAM showed as "cached" in TOP.

Ok thats fine now but what was earlier when it used to show ~800MB of RAM free most of the time ?
Any idea ?

gauravbajaj · « **Reply #1 on:** January 07, 2007, 06:21:24 PM »

Is the new hardisk containing any data in it?May be number of processes are taking more RAM now? but not sure why................? :?

I have no idea why its showing like this way? I am seeing this problem first time.

Plz share it if u will get the answer...........of your question

Any other Ideas Guys?

Gaurav

Ricky · « **Reply #2 on:** January 08, 2007, 10:16:08 AM »

Well, after posting this message I was still looking into many docs & those confirmed that LINUX try to use all free RAM to allocate frequently used data in RAM for faster access.
(BTW, that new disk was all new, even without any partitions)

Also, it was only evident on same day, and after late night and so on.. Its again showing eariler stats ie. around 800 MB RAM is free.

Once I was able to another situation where 400 mb RAM was free but server load ie . CPU usage etc. was around 1% only.

May be I need to know few more diagnosing tools or method.
Gaurave.. What you suggest ?

gauravbajaj · « **Reply #3 on:** January 09, 2007, 03:46:27 PM »

Hmm .you have to search it ......................, rlly its a different kind of problem........I will also search for it. and if wl update you if wl get any solution

Gaurav