Re: Performance degrade running on multicore computer

Hi,

I am using the PostgreSQL 8.4. What is the code path? After a row is
inserted to the table, it will update the fields of "validfrom", and
"validto". Followings are the table structure, data, and the performance
data:

xiliu=# \d page
Table "pyetlexa.page"
Column | Type | Modifiers
-----------------+-------------------+-----------
pageid | integer | not null
url | character varying |
size | integer |
validfrom | date |
validto | date |
version | integer |
domainid | integer |
serverversionid | integer |
Indexes:
"page_pkey" PRIMARY KEY, btree (pageid)
"url_version_idx" btree (url, version DESC)

Here is the data in this table:
http://imagebin.ca/img/KyxMDIKq.png

Here is the performance data by "top":
http://imagebin.ca/img/2ssw4wEQ.png

Regards,

afancy

On Sun, Nov 22, 2009 at 12:13 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> afancy <groupme(at)gmail(dot)com> writes:
> > My PostgreSQL server has two CPUs (OS: Fedora 11), each with 4 cores.
> Total
> > is 8cores. Now I have several clients running at the same time to do
> insert
> > and update on the same table, each client having its own connection. I
> have
> > made two testing with clients running in parallel to load 20M data in
> > total. Each testing, the data is split evenly by the client number such
> that
> > each client only loads a piece of data.
>
> What exactly are you doing when you "load data"? There are some code
> paths that are slower if they have to examine not-yet-committed tuples,
> and your report sounds a bit like that might be what's happening.
> But with so few details (not even a Postgres version number :-()
> it's difficult to be sure of anything.
>
> regards, tom lane
>