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I have a memory/cpu monitor running, and sometimes see the graph line for “cached memory” drop, for no apparent reason.

Earlier today Cache memory was at about 4.8GB but then dropped in two steps ( a small and a big ), to 2.3GB.

I was not deleting files, sometimes it happens when I run Baobab (disk usage analyser, a graphical recursive version of du).


Kernel is: Linux 2.6.32-5-686-bigmem


2013-jan-29 It did it again this time the amount dropped was a lot smaller than what was already free, so I don't think it is dropping it so that [some of] the memory can be used for something else.

sudden freeing of cache memory dark blue=buffers, red=application, green=cache, cyan=total

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Running Baobab or du requires a lot of individual files to be 'stat'ed. Perhaps an answer could be found in this direction. –  gertvdijk Jan 21 '13 at 14:04
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Where is the problem? ;) (I would say it is a good thing it sometimes flushes...) –  Rinzwind Jan 21 '13 at 14:07
    
@Rinzwind, Why, is it a good thing? To just forget stuff, that is still(I presume, 2GB of data did not suddenly stop existing) true. –  richard Jan 21 '13 at 15:14
    
@gertvdijk, Yes I expect that Baobab or du would stat lots of files and the data to be cached, thus causing the old data to be flushed. However the total should not drop my 2GB (or at all, except then a single object to be flushed is 2GB (do you think that is what it could be)). –  richard Jan 21 '13 at 15:22
    
I thought the objects of the cache where disk blocks. –  richard Jan 24 '13 at 10:49
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