Re: DBWR more active than its children

If 'more active' means 'using more CPU' then this is arguably reasonable. When you have multiple writers, dbwr takes a block and passes it to a child, the child writes it and informs dbwr.

The CPU cost of this activity is similar at both ends of the parent/child
dialogue, and the CPU cost to the child of invoking a write is not going
to make much difference. So if you have 8 children then dbwr is going
to be more busy than any of its children.

The benefit multiple db writers is that you gain reduced elapsed time by increasing concurrency - dbwr on its own can only work done a list of blocks serially: so time to write is proportional to number of blocks.
dbwr with 8 children can pass the blocks out 8 ways, and each child might be writing blocks to a different device - in the best possible case
the time to write is divided by the number of children. The cost is simply
the extra CPU overhead for the extra layer of memory handling. Received on Thu Sep 17 1998 - 11:24:23 CDT