Re: Spread checkpoint sync

Excerpts from Greg Smith's message of dom dic 05 20:02:48 -0300 2010:

> When ends up happening if you push toward fully sync I/O is the design 
> you see in some other databases, where you need multiple writer 
> processes.  Then requests for new pages can continue to allocate as 
> needed, while keeping any one write from blocking things.  That's one 
> sort of a way to simulate asynchronous I/O, and you can substitute true 
> async I/O instead in many of those implementations.  We didn't have much 
> luck with portability on async I/O when that was last experimented with, 
> and having multiple background writer processes seems like overkill; 
> that whole direction worries me.

Why would multiple bgwriter processes worry you?

Of course, it wouldn't work to have multiple processes trying to execute
a checkpoint simultaneously, but what if we separated the tasks so that
one process is in charge of checkpoints, and another oneZis in charge of
the LRU scan?

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Álvaro Herrera <alvherre@commandprompt.com>
The PostgreSQL Company - Command Prompt, Inc.
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