Re: Linux kernel impact on PostgreSQL performance

On Mon, Jan 13, 2014 at 5:32 PM, Jim Nasby <jim@nasby.net> wrote:
>>
>> That's my point. In terms of kernel-postgres interaction, it's fairly
>> simple.
>>
>> What's not so simple, is figuring out what policy to use. Remember,
>> you cannot tell the kernel to put some page in its page cache without
>> reading it or writing it. So, once you make the kernel forget a page,
>> evicting it from shared buffers becomes quite expensive.
>
>
> Well, if we were to collaborate with the kernel community on this then
> presumably we can do better than that for eviction... even to the extent of
> "here's some data from this range in this file. It's (clean|dirty). Put it
> in your cache. Just trust me on this."


If I had a kernel developer hat, I'd put it on to say: I don't think
allowing that last bit is wise for a kernel.

It would violate oh-so-many separation rules and open an oh-so-big can-o-worms.