| From: | Martijn van Oosterhout <kleptog(at)svana(dot)org> |
|---|---|
| To: | Gregory Stark <stark(at)enterprisedb(dot)com> |
| Cc: | Bruce Momjian <bruce(at)momjian(dot)us>, Heikki Linnakangas <heikki(at)enterprisedb(dot)com>, Russell Smith <mr-russ(at)pws(dot)com(dot)au>, Darcy Buskermolen <darcyb(at)commandprompt(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Alvaro Herrera <alvherre(at)commandprompt(dot)com>, "Matthew T(dot) O'Connor" <matthew(at)zeut(dot)net>, Pavan Deolasee <pavan(at)enterprisedb(dot)com>, Christopher Browne <cbbrowne(at)acm(dot)org>, pgsql-general(at)postgresql(dot)org, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: [HACKERS] Autovacuum Improvements |
| Date: | 2007-01-23 07:27:28 |
| Message-ID: | 20070123072727.GA19527@svana.org |
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| Lists: | pgsql-general pgsql-hackers |
On Mon, Jan 22, 2007 at 05:51:53PM +0000, Gregory Stark wrote:
> Actually no. A while back I did experiments to see how fast reading a file
> sequentially was compared to reading the same file sequentially but skipping
> x% of the blocks randomly. The results were surprising (to me) and depressing.
> The breakeven point was about 7%.
I asusume this means you were reading 7% of the blocks, not skipping 7%
of the blocks when you broke even?
I presume by break-even you mean it took just as long, time-wise. But
did it have the same effect on system load? If reading only 7% of the
blocks allows the drive to complete other requests more quickly then
it's beneficial, even if the vacuum takes longer.
This may be a silly thought, I'm not sure how drives handle multiple
requests...
Have a nice day,
--
Martijn van Oosterhout <kleptog(at)svana(dot)org> http://svana.org/kleptog/
> From each according to his ability. To each according to his ability to litigate.
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