Re: Up to date conventional wisdom re max shared_buffer size?

Hi,

On 2017-09-19 17:00:05 -0500, Jerry Sievers wrote:
> Briefly, just curious if legacy max values for shared_buffers have
> scaled up since 8G was like 25% of RAM?

It's very workload dependent. I've successfully used PG with roughly 1TB
of shared buffers, where that performed better than lower
settings.

> Pg 9.3 on monster 2T/192 CPU Xenial thrashing

Not sure what the word "thrashing" in that sentence means.

Things have improved a lot since 9.3 WRT to scalability, so I'd not
infer too much from 9.3 performance on a larger box.

> Upgrade pending but we recently started having $interesting performance
> issues at times looking like I/O slowness and other times apparently
> causing CPU spins.

That's not something we can really usefully comment on given the amount
of information.

> Anyway, shared_buffer coherency generally high but does take big dips
> that are sometimes sustained for seconds or even minutes.

"shared_buffer coherency"?

Greetings,

Andres Freund