Re: Separating bgwriter and checkpointer

On 20.09.2011 11:18, Simon Riggs wrote:
> The bgwriter avoids I/O, if it is operating correctly. This patch
> ensures it continues to operate even during heavy checkpoints. So it
> helps avoid extra I/O during a period of very high I/O activity.

I don't see what difference it makes which process does the I/O. If a 
write() by checkpointer process blocks, any write()s by the separate 
bgwriter process at that time will block too. If the I/O is not 
saturated, and the checkpoint write()s don't block, then even without 
this patch, the bgwriter process can handle its usual bgwriter duties 
during checkpoint just fine. (And if the I/O is not saturated, it's not 
an I/O bound system anyway.)

--   Heikki Linnakangas  EnterpriseDB   http://www.enterprisedb.com