The manpage says:
-k Lock down all paged memory. This is a somewhat
dangerous option
with large caches, so consult the README and memcached
homepage
for configuration suggestions.
README says:
Also, be warned that the -k (mlockall) option to memcached might be
dangerous when using a large cache. Just make sure the memcached
machines
don't swap. memcached does non-blocking network I/O, but not disk.
(it
should never go to disk, or you've lost the whole point of it)
Why locking pages in memory considered dangerous? It can avoid
swapping, so that keep a good response time. Doesn't it a good
feature?
