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.)
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