| From: | "Luke Lonergan" <llonergan(at)greenplum(dot)com> |
|---|---|
| To: | "Alex Turner" <armtuk(at)gmail(dot)com> |
| Cc: | "Dave Cramer" <pg(at)fastcrypt(dot)com>, "Greg Stark" <gsstark(at)mit(dot)edu>, "Joshua Marsh" <icub3d(at)gmail(dot)com>, pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: Hardware/OS recommendations for large databases ( |
| Date: | 2005-11-18 16:33:35 |
| Message-ID: | BFA3425F.1405B%llonergan@greenplum.com |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-performance |
Alex,
On 11/18/05 8:28 AM, "Alex Turner" <armtuk(at)gmail(dot)com> wrote:
> Ok - so I ran the same test on my system and get a total speed of
113MB/sec.
> Why is this? Why is the system so limited to around just
110MB/sec? I
> tuned read ahead up a bit, and my results improve a
bit..
OK! Now we're on the same page. Finally someone who actually tests!
Check the CPU usage while it's doing the scan. Know what it's doing?
Memory copies. We've profiled it extensively.
So - that's the suckage - throwing more CPU power helps a bit, but the
underlying issue is poorly optimized code in the Postgres executor and lack
of I/O asynchrony.
- Luke
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