Re: Help with a good mental model for estimating PostgreSQL throughput

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От David Ventimiglia
Тема Re: Help with a good mental model for estimating PostgreSQL throughput
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Msg-id CADE7j6hw_bjWWr6j7cm85QMJ_5B9Eq0qiAHQu+COcCaBneHLOQ@mail.gmail.com
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Ответ на Re: Help with a good mental model for estimating PostgreSQL throughput  (Laurenz Albe <laurenz.albe@cybertec.at>)
Ответы Re: Help with a good mental model for estimating PostgreSQL throughput
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Thanks!  Let's say there are 10 cores, the workload is not CPU bound, and there is a connection pooler like pgBouncer in place.  Would the number of operations more likely be:
  • 1000 ms / total ms per operation * number of cores = 1000 ms / 101 ms * 10 = ~100
  • 1000 ms / total ms per operation * number of connections = 1000 ms / 101 ms * 1000 = ~10000
  • something else
  • impossible to determine without more information
Best,
David

On Mon, Oct 30, 2023 at 8:46 AM Laurenz Albe <laurenz.albe@cybertec.at> wrote:
On Mon, 2023-10-30 at 08:05 -0700, David Ventimiglia wrote:
> Can someone help me develop a good mental model for estimating PostgreSQL throughput?
> Here's what I mean.  Suppose I have:
>  * 1000 connections
>  * typical query execution time of 1ms
>  * but additional network latency of 100ms
> What if at all would be an estimate of the number of operations that can be performed
> within 1 second?  My initial guess would be ~10000, but then perhaps I'm overlooking
> something.  I expect a more reliable figure would be obtained through testing, but
> I'm looking for an a priori back-of-the-envelope estimate.  Thanks!

It depends on the number of cores, if the workload is CPU bound.
If the workload is disk bound, look for the number of I/O requests a typical query
needs, and how many of them you can perform per second.

The network latency might well be a killer.

Use pgBouncer with transaction mode pooling.

Yours,
Laurenz Albe

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