Cannot allocate memory

Hi,

We have a problem where PostgreSQL will restart or shutdown when calling it through PDAL write filter. This was after we applied pgtune on the postgresql.conf.

These are the settings on the machine:
Virtual Machine - Ubuntu 13.10
1.92GB Memory
2 Parallel Processors

And these are the configurations from pgtune:
#------------------------------------------------------------------------------
# CUSTOMIZED OPTIONS
#------------------------------------------------------------------------------
default_statistics_target = 50 # pgtune wizard 2013-11-14
maintenance_work_mem = 112MB # pgtune wizard 2013-11-14
constraint_exclusion = on # pgtune wizard 2013-11-14
checkpoint_completion_target = 0.9 # pgtune wizard 2013-11-14
effective_cache_size = 1408MB # pgtune wizard 2013-11-14
work_mem = 11MB # pgtune wizard 2013-11-14
wal_buffers = 8MB # pgtune wizard 2013-11-14
checkpoint_segments = 16 # pgtune wizard 2013-11-14
shared_buffers = 448MB # pgtune wizard 2013-11-14
max_connections = 80 # pgtune wizard 2013-11-14

I have also set the shmmax to a higher value to adapt to the new configurations but it does not seem to solve the problem.

Below is a snippet of the postgresql.log:
2013-11-15 11:02:35 CET LOG: could not fork autovacuum worker process: Cannot allocate memory
2013-11-15 11:02:36 CET LOG: could not send data to client: Broken pipe
2013-11-15 11:02:36 CET LOG: unexpected EOF on client connection

Thanks

Zhi Feng