On 1/13/14, 2:37 PM, Claudio Freire wrote:
On Mon, Jan 13, 2014 at 5:32 PM, Jim Nasby <j...@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.
Yeah, if it were me I'd probably want to keep a hash of the page and it's
address and only accept putting a page back into the kernel if it matched my
hash. Otherwise you'd just have to treat it as a write.
--
Jim C. Nasby, Data Architect j...@nasby.net
512.569.9461 (cell) http://jim.nasby.net
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