How to reduce cached memory?
surenkarapetyan at gmail.com
Sat Feb 7 13:26:52 UTC 2009
Joshua C. wrote:
> 2009/2/7 Adrian Joian <adrian.joian at fedoraproject.ro>:
>> Well, if you really want to decrease cache levels you could at schedule
>> at random times the following command:
>> echo 1 > /proc/sys/vm/drop_caches
>> Adrian JOIAN
>> Chris Tyler wrote:
>>> On Fri, 2009-02-06 at 23:57 +0100, Joshua C. wrote:
>>>> I have kde 4.2 and f9. After 2+ hours on my computer it has about
>>>> 1,4GB cached memory. I don't see him releasing this memory after time.
>>>> I know it comes from the apps being open but it seems the kernel
>>>> "never" releases the memory after the app terminates. How to make the
>>>> kernel free this memory? I've seen similar cases with kde 3.5.10 and
>>>> f8 and f7. I know kde eats memory but this is too much. Who caches so
>>>> much of it? Why?
>>>> The mashine has 2,6 GB RAM (still x86) and 512mb swap which is rarely
>>>> used (~ 50mb at most) and combined cached + app memory totals about 2
>>> Hi Joshua,
>>> Memory is being used for cache basically because it's not being used for
>>> anything else. The kernel will gladly use that memory for other purposes
>>> when it's needed -- but until then, there's no harm in keeping disk data
>>> around in otherwise-unused memory just in case it's needed later.
>>> This is why the "free" command shows a "-/+ buffers/cache" line, which
>>> shows you what the memory picture is without the cache (i.e., the memory
>>> that is truly available when needed):
>>> $ free
>>> total used free shared buffers cached
>>> Mem: 4061388 3796632 264756 0 259244 570224
>>> -/+ buffers/cache: 2967164 1094224
>>> Swap: 4194296 2092276 2102020
>> fedora-devel-list mailing list
>> fedora-devel-list at redhat.com
> Than you everyone for the replies. Swapping do occurs (although
> rarely) but this is not my concern. What I don't like is the fact,
> that the kernel fills the memory with "what he thinks I would use/like
> or have already used". I didn't know it will use the cached memory in
> case it's needed.
> But then is the question: When swapping occurs where have the other
> 2,6 gb ram gone? I don't believe I've opened so many apps that can
> consume so much memory.
That's another aspect of linux VM subsystem (read:
To be short, kernel decides to swap out unused program pages from
physical memory to the disk.
This clears physical memory for cache use.
Example: You open OOo Writer and leave it alone for half an hour.
Kernel decides You aren't going to use it soon, and swaps (all) it's
That gives the kernel additional ~100 MBs to cache the movie You're
editing in Kino.
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