Re: WIP: Fast GiST index build

On Sat, Jun 25, 2011 at 11:03 AM, Jesper Krogh <jesper(at)krogh(dot)cc> wrote:

> * Wouldn't it be natural to measure the performance benefits of
> disc-bound tests in an SSD setup?
>
Sure, it would be great to run performance tests on SSD drives too.
Unfortunately, I don't have corresponding test platform just now.

... my understanding of Fast gi(n|st) index build is that it is
> more or less a challenge to transform a lot of random IO workload
> to be more sequential and collapse multiple changes into fewer.
>
The main benefit of proposed algorithm is to greatly reduce number IO
operations during index build due to dealing with great number of index
tuples simultaneously. And it also makes some IO more sequential. I haven't
precise measures yet, but I belive that contribution of making IO more
sequantial is not very significant.

> In terms of random IO an SSD can easily be x100 better than rotating
> drives and it would be a shame to optimize "against" that world?
>
Actually, I'm not sure that IO is bottle neck of GiST index build on SSD
drives. It's more likely for me that CPU becomes a bottle neck in this case
and optimizing IO can't give much benefit. But anyway, the value of this
work can be in producing better index in some cases and SSD drive lifetime
economy due to less IO operations.

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With best regards,
Alexander Korotkov.