Re: Multi CPU Queries - Feedback and/or suggestions wanted!

Jonah H. Harris wrote:
> fadvise is a kludge.

I don't think it's a kludge at all. posix_fadvise() is a pretty nice and 
clean interface to hint the kernel what pages you're going to access in 
the near future. I can't immediately come up with a cleaner interface to 
do that.

Compared to async I/O, it's helluva lot simpler to add a few 
posix_fadvise() calls to an application, than switch to a completely 
different paradigm. And while posix_fadvise() is just a hint, allowing 
the OS to prioritize accordingly, all async I/O requests look the same.

>  While it will help, it still makes us completely
> reliant on the OS.

That's not a bad thing in my opinion. The OS knows the I/O hardware, 
disk layout, utilization, and so forth, and is in a much better position 
to do I/O scheduling than a user process. The only advantage a user 
process has is that it knows better what pages it's going to need, and 
posix_fadvise() is a good interface to let the user process tell the 
kernel that.

> IIRC, we currently have support for rings in the buffer pool, which we could read
> directly into.

The rings won't help you a bit. It's just a different way to choose 
victim buffers.

--   Heikki Linnakangas  EnterpriseDB   http://www.enterprisedb.com