| From: | Michael Stone <mstone+postgres(at)mathom(dot)us> |
|---|---|
| To: | Luke Lonergan <LLonergan(at)greenplum(dot)com> |
| Cc: | pgsql-hackers(at)postgresql(dot)org, pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: [HACKERS] A Better External Sort? |
| Date: | 2005-10-05 15:33:49 |
| Message-ID: | 20051005153349.GZ2241@mathom.us |
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| Lists: | pgsql-hackers pgsql-performance |
On Wed, Oct 05, 2005 at 11:24:07AM -0400, Luke Lonergan wrote:
>Nope - it would be disk wait.
I said I/O overhead; i.e., it could be the overhead of calling the
kernel for I/O's. E.g., the following process is having I/O problems:
time dd if=/dev/sdc of=/dev/null bs=1 count=10000000
10000000+0 records in
10000000+0 records out
10000000 bytes transferred in 8.887845 seconds (1125132 bytes/sec)
real 0m8.889s
user 0m0.877s
sys 0m8.010s
it's not in disk wait state (in fact the whole read was cached) but it's
only getting 1MB/s.
Mike Stone
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