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Re: Apparent deadlock for simultaneous sequential scans

From: bruc(at)stone(dot)congenomics(dot)com (Robert E(dot) Bruccoleri)
To: tgl(at)sss(dot)pgh(dot)pa(dot)us (Tom Lane)
Cc: pgsql-bugs(at)postgresql(dot)org
Subject: Re: Apparent deadlock for simultaneous sequential scans
Date: 2001-06-08 13:32:38
Message-ID: 200106081332.JAA70934@stone.congenomics.com (view raw or flat)
Thread:
Lists: pgsql-bugs
Dear Tom,
> 
> 
> pgsql-bugs(at)postgresql(dot)org writes:
> > Apparent deadlock for simultaneous sequential scans
> 
> > However, if more than one application is run at once, the performance
> > deteriotates drastically.
> 
> So is it a deadlock, or a slowdown?  How many is "more than one"?

With two processors running the same query, it appears to be a
slowdown.  When I look at the system calls, the backends were
executing about one read per second. With six processors running the
same query, it appeared to be a deadlock -- no I/O's were being issued
over the time that I watched.

"More than one" means two or more.

Thanks. --Bob

+----------------------------------+------------------------------------+
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| President, Congenomics, Inc.     | Fax:   609 737 7528                |
| 114 W Franklin Ave, Suite K1,4,5 | email: bruc(at)acm(dot)org                |
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