Re: Impact of checkpoint_segments under continual load conditions

On 7/19/05, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Christopher Petrilli <petrilli@gmail.com> writes:
> > As I'm doing this, I'm noticing something *VERY* disturbing to me:
> > postmaster backend: 20.3% CPU
> > psql frontend: 61.2% CPU
>
> > WTF?  The only thing going through the front end is the COPY command,
> > and it's sent to the backend to read from a file?
>
> Are you sure the backend is reading directly from the file, and not
> through psql?  (\copy, or COPY FROM STDIN, would go through psql.)

The exact command is:

COPY test (columnlist...) FROM '/tmp/loadfile';

> But even so that seems awfully high, considering how little work psql
> has to do compared to the backend.  Has anyone ever profiled psql doing
> this sort of thing?  I know I've spent all my time looking at the
> backend ...

Linux 2.6, ext3, data=writeback

It's flipped now (stil lrunning), and it's 48% postmaster, 36% psql,
but anything more than 1-2% seems absurd.

Chris
--
| Christopher Petrilli
| petrilli@gmail.com