Cache Memory in top command

Bas Smeelen b.smeelen at
Wed Sep 29 12:41:19 UTC 2010

On 09/29/2010 01:42 PM, Bruce Cran wrote:
> On Wed, 29 Sep 2010 08:57:09 +0200
> Bas Smeelen <b.smeelen at> wrote:
>>  *Cache:* number of clean pages caching data that are available for
>> immediate reallocation
>> <>
> I believe the "Cache" value is almost totally unrelated to the
> amount of memory used for caching: FreeBSD has a unified buffer cache
> so any memory is available for use as cache. Unlike Linux, you can't
> look at the line in 'top' to see how much memory is being used for
> buffers and cache.
> You can find more information about the VM architecture at
> .
The way I understand it:
The amount of cached file data pages is included in the Wired value
The amount of free cache pages that can immediatly can be re-used for
caching is the Cache value
The Buf value is the numbder of pages used for BIO-level disk caching
I think that the value of Inactive also includes some kind of
application data cache
So as you also state, unlike linux there is no way of determining the
amount of memory used for *all caching* with top

For more info of basic design decisions I think this is a good resource

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