Red Hat memory allocation

[David Tonhofer, m-plify S.A.]

I will start off here and say that it is expected behaviour
for Linux to eat up all memory: everything that is 'not really
needed' will be used as cache. Here are my numbers. Note the
3.29% "free" RAM. This machine has currently no charge:


Total mem w/o kernel:      9380832 KB
|  |--Free:                6392904 KB (68.15%)
|  `--Used:                2987928 KB
|--Swap mem:               6291440 KB
|  |--Free:                6291280 KB (100.00%)
|  `--Used:                    160 KB
|     `--SwapCached:             0 KB (0.00%)
`--Dynamic mem:            3089392 KB
   |--Free:                 101624 KB (3.29%) <--- AHA
   `--Used:                2987768 KB
      |--Allocated:         827000 KB (27.68%)
      |  |--Floating:        -8016 KB
      |  |--Slab:           435988 KB (52.72%)
      |  |--Page tables:      5828 KB (0.70%)
      |  `--Mapped:         393200 KB (47.55%)
      |     ~RSS sum:       519784 KB (132.19%)
      `--Caching:          2160768 KB
         |--Buffer cache:   436108 KB
         `--Page cache:    1724660 KB


There are still a lot of things that are mysterious to me
in Linux' memory allocation of course and the above tree
may not reflect reality underneath 'Allocated'.



--On Thursday, October 13, 2005 11:51 AM -0700 "Yard, John" <jyard at ais.ucla.edu> wrote:

>
> On a Red Hat 3.2 system running Sun Directory Server
> Sun DS had a virtual memory failure and hung
> while I was running a system stress test.
>
> The test involved running 30 DS entry scans.
>
> I noticed that the steady-state memory behavior of the system
> leaves only 1% or less of the system memory in the free pool:
>
> eds2:/root] # vmstat 1
> procs                      memory      swap          io     system
> cpu
>  r  b   swpd   free   buff  cache   si   so    bi    bo   in    cs us sy
> wa id
>  0  0      0 115600 273828 5364176    0    0     0     2    1     2  0
> 0  0  3
>  0  0      0 115600 273828 5364180    0    0     0    52  191   142  0
> 0  0 100
>  0  0      0 115600 273828 5364180    0    0     0     0  178   134  0
> 0  0 100
>  0  0      0 115600 273828 5364180    0    0     0     0  180   111  0
> 0  0 100
>
> Most systems I am aware of recommend 10%-15% of memory
> on the free pool as a low-water mark.
>
> I think I need to set the steady state free pool at ~10%.
>
> Am I on the right track ?
> How do I do this ?
>
> JYard
> UCLA
>
> --
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