HOWTO: Clear filesystem memory cache

[matt_symes]

Hi

To be more specific, programs stop responding, and the GUI freezes up from time to time. I know that the problem is tied to firefox; perhaps a plugin. However if I disable all of the plugins and restart firefox, I don't get 'all' of my memory back.

In other words, if I start off at 30% of Ram and it creeps up to 80% after a few hours, if I disable all plugins (other than google talk) and restart firefox I might now be at 55%.

I finally made it down to PCExpress and just bought a couple more Gigs of DDR2 800 RAM. We'll see what happens in a few hours. I started out at 20% about two hours ago and now I'm at 28%. Now 'that's' nothing to be concerned about.

I'll keep watching it though. Maybe 10.04 just doesn't like hanging out with less than 4Gigs of RAM

Maybe you have a memory leak.

That would be a different issue than the issue highlighted by psusi. I like my caches flaming hot. I would prefer my memory refresh cycles to refresh data that i might need as opposed to refreshing it for data that i definitely won't need as it's not there.

I have 3GB ram on my laptop and 10.04 flies along.

Kind regards

[psusi]

In other words, if I start off at 30% of Ram and it creeps up to 80% after a few hours, if I disable all plugins (other than google talk) and restart firefox I might now be at 55%.

As measured how? If you are counting the cache in that figure, then that is perfectly normal.

[tg3793]

As measured how? If you are counting the cache in that figure, then that is perfectly normal.

I wouldn't disagree that it "creeping up" to 80% or more isn't normal. But it's the not being able to flush it in any way shape or form (other than a reboot) that I wouldn't consider normal.

And, as I had mentioned before, I'm measuring the memory usage with "free -m".

[tg3793]

I mostly continuing this thread out of a curiosity to learn at this point. Ever since I added an extra 2Gig memory module I haven't had a problem Nice snappy system with several hours of use going from 20% usage to 53% usage.

Still a problem that I can't "flush the memory" to get back down to the pre-boot 20% usage. But since the system continues to be nice and snappy I have no really need to now :-)

This latest development seems to validate my general statement of "when it works it works, and when it doesn't it doesn't" ... Ok, well that's not very scientific so I'll "frame" it another way. It seems that there is a memory leak in firefox (most likely one of the plugins) that gradually eats up memory even when pushing the upper limit as hight as 95% to 98% memory usage. And when it starts to get that high the system really starts to choke.

I'm using Ubuntu 10.04 and I understand that the memory management 'should' prevent this by pushing some of this to SWAP (how much or when I haven't researched yet).

Now that I've added 2Gig of RAM (total of 4Gig now) I am still having the memory leak issue but the speed of the memory leak has remained stable. This has allowed me to continue operating at a nice snappy speed even at eighteen hours of operation. I'll continue monitoring usage and see if the memory leak grows at this steady rate thereby eating all of the four gig (just taking longer to do so).

Again I don't know if it will eat the additional memory, I'm simply going to continue watching it. I'll report back here later for the edification of anyone interested :-)

[matt_symes]

Hi

@tg3793

This is old but the general principles still apply.

http://tldp.org/LDP/tlk/mm/memory.html

BTW: It just works on my machine. Have a look at the kernel source if you want to know how memory management is handled now.

Kind regards

[tg3793]

This is old but the general principles still apply.
http://tldp.org/LDP/tlk/mm/memory.html

Thanks; good information.

BTW: It just works on my machine.

:-)

[psusi]

I wouldn't disagree that it "creeping up" to 80% or more isn't normal. But it's the not being able to flush it in any way shape or form (other than a reboot) that I wouldn't consider normal.

And, as I had mentioned before, I'm measuring the memory usage with "free -m".

But which column? The +/- cache or not? If it is not the +/- cache, then you can clear it as this thread describes, but shouldn't because that "used memory" is doing good. If it is the +/- cache line, then check the system monitor or top to see what program is hogging it all and kill it.

total used free shared buffers cached
Mem: 3939 3537 402 0 60 2035
-/+ buffers/cache: 1441 2497

The 3537 might look like a lot, but since 2035 of it is cache, there is not a problem. It is the 1441/2497 numbers you want to look at.

[Catalyph]

My NAS server was running very slow and slow transfer speeds over the network was getting 30 - 40 MB/s when i usually get 90+ MB/s when I ssh into the machine it indicated 96.8 % mem usage out of 2GB RAM.

I used the command by logging in as root.

sudo su
sync
echo > 3 /proc/sys/vm/drop_caches

now my system is working as normal and mem usage is back down to only 12%

Thanks!

[pooneh2201]

Hi guys! This doesn't seem to work in 10.04. I get

bash: /proc/sys/vm/drop_caches: Permission denied

I am not well versed in the terminal and have only been using linux for a couple of months now. I am using PAE with 6 gb of ram. Hope you guys can help. Oh, and the system monitor shows full memory cache use.

use sudo command at first of the line ,

[sayed100100]

hello my frinds ihave some problem Clearing cached memory on Linux system


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