Is there a way to tell mongodump or mongod to that effect, to free the current used ram?
I have an instance with a Mongo DB server which has a couple of databases which total around 2GB. The instance has 5GB of ram. Every night I have a backup cron running mongodump. I have set up a 5GB swap file. Every other night the OOM-Killer will kill mongo, the memory will go down to ~30% and spike up to again ~60% at backup time and stays like that until next backup spikes up the memory and OOM-Killer kicks in.
Before this I had like 3.75GB and no swap and it was getting killed every night and sometimes during the day when usted. I added more ram and the swap file a few days ago, and it has improved, but still is getting killed every other day and the memory after the backup is at ~60%. And I'm paying for extra ram that is only used for these spikes at backup.
If I run mongostat I see that mongo increases the used ram during backup but does frees it afterward. Is there a way to free it? Something that will not be to stop and start mongod ?
Before Backup:
insert query update delete getmore command dirty used flushes vsize res qrw arw net_in net_out conn time
*0 *0 *0 *0 0 3|0 0.0% 1.0% 0 1.10G 100M 0|0 1|0 212b 71.0k 3 May 3 16:14:41.461
During backup:
insert query update delete getmore command dirty used flushes vsize res qrw arw net_in net_out conn time
*0 *0 *0 *0 1 1|0 0.0% 81.2% 0 2.61G 1.55G 0|0 2|0 348b 33.5m 7 May 3 16:16:01.464
After Backup
insert query update delete getmore command dirty used flushes vsize res qrw arw net_in net_out conn time
*0 *0 *0 *0 0 2|0 0.0% 79.7% 0 2.65G 1.62G 0|0 1|0 158b 71.1k 4 May 3 16:29:18.015