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Old 03-04-2003, 11:27 AM   #1
chewy
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Red Hat Memory Utilization


I've noticed with Red Hat 7.3 and 8.0 that top and free report almost 100% of the physical RAM in my box is in use. For example: boot into rc3, after boot 55 process running roughly 60 mg of ram top reports as in use. Run top 8 hrs later, 124 mg of ram in use, same 55 processes running. My question is, does RH cache available memory, which commands like top and free show as physical memory in use?
 
Old 03-04-2003, 12:21 PM   #2
Q*Bert
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Hello chewy, welcome to LQ.org.

If you like, post the output of

ps -aux > output.txt

here, and we can see what services you're running which you don't need. BTW there's no inherent security risk in showing us the output of ps -aux - just so you feel safe.

Q*Bert
 
Old 03-05-2003, 05:50 PM   #3
kaiserfro
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Yep. On a fresh boot up usually you'll see that ram is mostly free...but linux uses RAM to cache up filesystems. If you have one of those cool little programs that indicate for RAM usage (top, free, or x equiv) you'll see that things start with low ram usage and low cached data.

All you have to do is a copy of a large file and BAM are your ram gets sucked up. Watch the RAM usage go up and the cached data go up.

Not to worry though. If the system needs memory for user programs, it will writeback the cached info back to the physical device and allow that ram to be freed.
 
Old 03-05-2003, 07:22 PM   #4
Q*Bert
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I'm having a real problem with Redhat 8.0 and memory at the moment. I've been reading that others have the problem too - it seems to be the well documented kswapd bug.

When the system transfers large files the swap suddenly starts thrashing and won't stop. And it *really* slows the system right down to the point where it's completely unusable. Even the login stops working (times out).

It happens consistently when large files are copied between directories, and frankly, this bug is a real liability.

I'm not happy.

Q*Bert
 
  


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