Messages in this thread | | | Date | Wed, 4 Mar 2009 18:04:20 +0800 | From | Wu Fengguang <> | Subject | Re: drop_caches ... |
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Hi Markus,
On Wed, Mar 04, 2009 at 10:57:33AM +0100, Markus wrote: > Hello! > > I have a small problem. Maybe its just a misunderstanding but I cant > solve it. > > I think that writing "3" to drop_caches should drop all buffers and > caches which are already written. So its recommended to put a "sync" > infront of it. > So I did "free -m ; sync ; echo 3 > /proc/sys/vm/drop_caches ; free -m" > And it gave me: > total used free shared buffers > cached > Mem: 3950 3922 28 0 1 > 879 > -/+ buffers/cache: 3041 909 > Swap: 5342 205 5136 > total used free shared buffers > cached > Mem: 3950 3907 43 0 0 > 864 > -/+ buffers/cache: 3041 908 > Swap: 5341 206 5135 > > So the buffer was 1 and is 0 afterthat. But cached is at 879 MB before > and is still 864 MB (!!!) after that! > > I am at swappiness=0 and when I remove and readd one swap-partition > after another (so there is always swap). It will keep the cached and > put the swapped memory on other swaps?! > > I _think_ thats not the way it should go? > > It would be really kind if someone could explain that issue and > what "cached" is at all!
The memory mapped pages won't be dropped in this way. "cat /proc/meminfo" will show you the number of mapped pages.
Thanks, Fengguang
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