Possible memory leak in mon?

[Vladimir Bashkirtsev <vladimir@bashkirtsev.com>]

Dear devs,

I have three mons and two of them suddenly consumed around 4G of RAM 
while third one happily lived with 150M. This immediately prompts few 
questions:

1. What is expected memory use of mon? I believed that mon merely 
directs clients to relevant OSDs and should not consume a lot of 
resources - please correct me if I am wrong.
2. In both cases where mon consumed a lot of memory it was preceded by 
disk-full condition and both machines where incidents happened are 64 
bit, rest of cluster 32 bit. mon fs and log files happened to be in the 
same partition - ceph osd produced a lot of messages, filled up disk, 
mon crashed (no core as disk was full), manually deleted logs, restarted 
mon without any issue, some time later found mon using 4G of RAM. 
Running 0.45. Should I deliberately recreate conditions and crash mon to 
get more debug info (if you need it of course, and if yes then what)?
3. Does figure 4G per process coming from 32 bit pointers in mon? Or mon 
potentially can consume more than 4G?
4. I guess it is good idea to keep mon fs on separate partition so it 
would not experience disk-full state. Currently it is around 80Mb while 
whole ceph 42% full of 2100Gb with 6 OSDs and 600 pgs. Can you provide 
some idea how to estimate mon fs size?

Regards,
Vladimir