cached - any tools to explain what has been cached on linux

Daniel Son dsong-ieW52yutvQFg9hUCZPvPmw at public.gmane.org
Thu Oct 18 18:44:06 UTC 2007


Also interesting reading on this subject:

http://sourcefrog.net/weblog/software/linux-kernel/free-mem.html

and

also slabtop command or /proc/slabinfo (harder to read), can give you 
info about active caches. The total cache size still will be way below 
what 'top' shows, but the above link gives some good explanation why.

D



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Lennart Sorensen wrote:
> On Sun, Oct 14, 2007 at 05:33:05PM -0400, tleslie wrote:
>   
>> I set up a machine with postgres,
>> and a 16GB of RAM and its really quick as compared to
>> a similar machine running postgres with similar DB
>> and only 3GB RAM.
>>
>> Does anyone know of any utils or profiling tools
>> that would explain what the cache in linux
>> is doing?
>>
>> TOP: 
>>
>> Mem:  16440144k total, 12889668k used,  3550476k free,    69076k buffers
>> Swap:  2104472k total,    10732k used,  2093740k free, 10203404k cached
>>
>> i'd love to know how/what is in that 10 GB of cache
>>
>> i know it stores allocation blocks for programs to use, but its
>> got to be so much more then that.
>>     
>
> Disk cache. :)  So even if postgres only uses a bit of ram itself, the
> whole database might end up read into ram, so only writes have to go to
> disk.  That would be rather fast.
>
> --
> Len Sorensen
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