Re: shared_buffers advice

2010/5/27 Konrad Garus <konrad.garus@gmail.com>:
> 2010/5/27 Cédric Villemain <cedric.villemain.debian@gmail.com>:
>
>> It works thanks to mincore/posix_fadvise stuff : you need linux.
>> It is stable enough in my own experiment. I did use it for debugging
>> purpose in production servers with succes.
>
> What impact does it have on performance?

pgmincore() and pgmincore_snapshot() both are able to mmap up to 1GB.
I didn't mesure a performance impact. But I haven't enough benchmarks/test yet.

>
> Does it do anything, is there any interaction between it and PG/OS,
> when it's not executing a command explicitly invoked by me?

pgfincore does nothing until you call one of the functions.

Reducing the mmap window is faisable, and I had start something to use
effective_io_concurrency in order to improve prefetch (for restore)
but this part of the code is not yet finished.

>
> --
> Konrad Garus
>



--
Cédric Villemain               2ndQuadrant
http://2ndQuadrant.fr/     PostgreSQL : Expertise, Formation et Support