Re: Questions about checksum feature in 9.3

On 9/16/13 10:14 AM, David Johnston wrote:
> The "single" core aspect is interesting. Does the implementation have a
> dedicated core to perform these calculations or must the same thread that
> handles the relevant query perform this work as well? How much additional
> impact/overhead does having to multitask have on the maximum throughput of a
> single core in processing checksums?

Postgres doesn't currently have any real kind of parallelism, so whatever process needs to do the checksum will be the process actually running the checksum.

That said, there are background processes that could potentially be involved here, depending on exactly where checksums are being calculated (I don't remember exactly when the checks are done). For example, if a buffer is being written out by the bgwriter, then it's the bgwriter process that will actually do the checksum, not a backend process.
--
Jim C. Nasby, Data Architect jim(at)nasby(dot)net
512.569.9461 (cell) http://jim.nasby.net