Re: Could we replace SysV semaphores with latches?

On 06/07/2012 06:09 AM, Tom Lane wrote:
> There has been regular griping in this list about our dependence on SysV
> shared memory, but not so much about SysV semaphores, even though the
> latter cause their fair share of issues; as seen for example in
> buildfarm member spoonbill's recent string of failures:
> 
> creating template1 database in /home/pgbuild/pgbuildfarm/HEAD/pgsql.25563/src/test/regress/./tmp_check/data/base/1
...FATAL:  could not create semaphores: No space left on device
 
> DETAIL:  Failed system call was semget(1, 17, 03600).
> HINT:  This error does *not* mean that you have run out of disk space.  It occurs when either the system limit for
themaximum number of semaphore sets (SEMMNI), or the system wide maximum number of semaphores (SEMMNS), would be
exceeded. You need to raise the respective kernel parameter.  Alternatively, reduce PostgreSQL's consumption of
semaphoresby reducing its max_connections parameter.
 
>     The PostgreSQL documentation contains more information about configuring your system for PostgreSQL.
> child process exited with exit code 1

hmm now that you mention that I missed the issue completely - the
problem here is that spoonbill only has resources for one running
postmaster and the failure on 24.5.2012 caused a left over postmaster
instance - should be fixed now


Stefan