Re: 8.4 open item: copy performance regression?

Tom Lane <tgl@sss.pgh.pa.us> wrote:

> It'd be useful first off to figure out if it's a CPU or I/O issue.
> Is there any visible difference in vmstat output?  Also, try turning
> off autovacuum in both cases, just to see if that's related.

Both took slightly longer with autovacuum off, but probably just
within the noise.

It's hard to interpret the vmstat output, largely because I chose to
run this on one of our biggest servers, which is not currently serving
an application, per se, but as a replication target, and this being
"off hours" is busy running the sync process to the source machines.
This involves generating md5 sums on both sides for blocks of rows,
which is pretty CPU-intensive.  There is very little disk output from
that right now, pretty light on the disk reads, but keeping a few CPUs
pretty busy generating those md5 sums.

I've got to go keep an appointment, but I'll come back and see if I
can do more.  For now, here's the raw vmstat, in case someone can pick
out info I'm missing:

-Kevin