2.4.20 page cache information

2.4.20 page cache information

[kernwek jalsl]

Hello Everyone;

On my embedded system having 64MB of RAM and no swap,
I see the  following information on opening
/proc/meminfo:

       total:    used:    free:  shared: buffers: 
cached:
Mem:  62894080 47947776 14946304        0  4964352
23674880
Swap:        0        0        0
MemTotal:        61420 kB
MemFree:         14596 kB
MemShared:           0 kB
Buffers:          4848 kB
Cached:          23120 kB
SwapCached:          0 kB
Active:          32340 kB
ActiveAnon:      10760 kB
ActiveCache:     21580 kB
Inact_dirty:         0 kB
Inact_laundry:    6336 kB
Inact_clean:       236 kB
Inact_target:     7780 kB
HighTotal:           0 kB
HighFree:            0 kB
LowTotal:        61420 kB
LowFree:         14596 kB
SwapTotal:           0 kB
SwapFree:            0 kB

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?

Thanks in advance
Editya

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Rmap was: 2.4.20 page cache information

[Mike Fedyk]

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?