[CentOS] Trouble with Mailman

Sun Nov 13 23:37:41 UTC 2011
Yves Bellefeuille <yan at storm.ca>

On Sunday 13 November 2011 08:32, John J. Boyer wrote:

> Why does Linux do this? It seems odd to me.

Suppose you have 4 Gb of RAM, of which only 1 Gb is used. What good is 
the other 3 Gb doing you? You might as well not have it at all.

Instead of leaving the RAM unused, Linux uses it as a cache. It can't 
hurt, and it can help. If a programme needs the memory, Linux will make 
it available to the programme quickly enough.

"free" gives me the following report:

$ free
             total      used      free    shared   buffers    cached
Mem:       4147456   3991600    155856         0     98556   2739992
-/+ buffers/cache:   1153052   2994404
Swap:      3911788       248   3911540

Therefore, I have 4 Gb of RAM, of which about 1 Gb is used for the 
programmes and a little under 3 Gb is used as a cache.

Apparently Windows finally decided to use a similar approach, which it 
calls SuperFetch.

I'm not sure how to disable the cache entirely, but to clear it, with  
kernel 2.6.16 or later, do the following as root:

sync ; echo 3 > /proc/sys/vm/drop_caches

Yves Bellefeuille <yan at storm.ca>
"La Esperanta Civito ne rifuzas anticipe la kunlaboron de erarintoj, se
ili konscias pri sia eraro." -- Heroldo Komunikas, n-ro 473.