Rmap was: 2.4.20 page cache information

From: Mike Fedyk
Date: Tue Dec 02 2003 - 13:34:36 EST


On Tue, Dec 02, 2003 at 04:33:23AM -0800, kernwek jalsl wrote:
> Hello Everyone;
>
> On my embedded system having 64MB of RAM and no swap,
> I see the following information on opening
> /proc/meminfo:
>

Everything goes through the page cache, including all of your apps. The
executables are mapped through the page cache, cache is combined with
executable data.

And you have a kernel patched with the rmap VM.

All numbers are seperate below:

> total: used: free: shared: buffers:
> cached:
> Mem: 62894080 47947776 14946304 0 4964352
> 23674880
> Swap: 0 0 0
> MemTotal: 61420 kB

MemTotal =

> MemFree: 14596 kB
> Active: 32340 kB
> Inact_dirty: 0 kB
> Inact_laundry: 6336 kB
> Inact_clean: 236 kB
> Inact_target: 7780 kB

Not sure why Inact_target is in there, but it adds up almost perfect to
memtotal.

These below are within the active/inactive lists:

> MemShared: 0 kB
> Buffers: 4848 kB
> Cached: 23120 kB
> SwapCached: 0 kB

> ActiveAnon: 10760 kB
> ActiveCache: 21580 kB

Remember, that's active. If it's not active, then it's in the inactive
list. And it doesn't show inactive_anon memory (because it's not on a
seperate list)

> HighTotal: 0 kB
> HighFree: 0 kB
> LowTotal: 61420 kB
> LowFree: 14596 kB
> SwapTotal: 0 kB
> SwapFree: 0 kB
>

Don't try adding the numbers on stock 2.4, they're just not fully accounted
in /proc/meminfo, but with rmap you can get close.

> As I see the total memory belonging to page cache is
> 23MB and the anonymous list is 10MB. But if I count
> the RSS values for all the processes running on the
> system, it hardly comes to 15MB. Where is the rest of
> the 18MB? If I understand the "cached:" = (pages in
> the page cache - buffer cache). Even if I am doing
> lots of file activity; I cannot imagine the file
> system reads and writes holding up 18MB of the page
> cache. Am I missing something here?

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