Strange memory management behavior

[Ivan Krstic]

All,

I've recently run into some strange memcached behavior, and didn't see 
it mentioned in the list archives. I have an 800 MB memcached process 
which is taking up about a gig of ram, but only using ~577MB:

nobody   12704  1.8 45.8 958100 951160 ?     S<   Feb10  26:05
  (/usr/local/bin/memcached -d -m 800 -p 11000 -u nobody)

STAT uptime 85218
STAT version 1.1.11
STAT rusage_user 613:800688
STAT rusage_system 951:754311
STAT curr_items 544412
STAT total_items 3407507
STAT bytes 577981537
STAT curr_connections 1136
STAT total_connections 765713
STAT connection_structures 11546
STAT cmd_get 12278259
STAT cmd_set 3407554
STAT get_hits 11407497
STAT get_misses 870762
STAT bytes_read 4137592615
STAT bytes_written 18351838993
STAT limit_maxbytes 838860800

New sets seem to push old keys out of LRU queues, even though there 
should still be plenty of RAM to go around. Does someone have an idea 
why this is so?

Cheers,
Ivan