Re: Experimental ARC implementation

Jan Wieck wrote:
> It also contains the starting work of the discussed background buffer
> writer. Thus far, the BufferSync() done at a checkpoint only writes out
> all dirty blocks in their LRU order and over a configurable time
> (lazy_checkpoint_time in seconds). But that means at least, while the
> checkpoint is running the backends should not need to flush dirty
> buffers as well, since all the candidates they get for replacement are
> clean. My plan is to create another background process very similar to
> the checkpointer and to let that run forever basically looping over that
> BufferSync() with a bool telling that it's the bg_writer.

Have you considered having the background writer check the pages it is
about to write to see if they can be added to the FSM, thereby reducing
the need for vacuum? Seems we would need to add a statistics parameter
so pg_autovacuum would know how many tuples the background write added
to the freespace map, so it doesn't vacuum a table that doesn't need it.

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