Re: [Lsf-pc] Linux kernel impact on PostgreSQL performance

On 1/13/14, 4:47 PM, Jan Kara wrote:
> Note to postgres guys: I think you should have a look at the proposed
> 'vrange' system call. The latest posting is here:
> http://www.spinics.net/lists/linux-mm/msg67328.html. It contains a rather
> detailed description of the feature. And if the feature looks good to you,
> you can add your 'me to' plus if anyone would be willing to try that out
> with postgress that would be most welcome (although I understand you might
> not want to burn your time on experimental kernel feature).

I don't think that would help us with buffers unless we switched to MMAP (which is a huge change), but this part is interesting:

"* Opportunistic freeing of memory that may be quickly reused. Minchan
has done a malloc implementation where free() marks the pages as
volatile, allowing the kernel to reclaim under pressure. This avoids the
unmapping and remapping of anonymous pages on free/malloc."

Postgres has it's own memory management on top of malloc that gives us memory contexts; some of those contexts get destroyed frequently. Allowing the kernel to reclaim that free'd memory in the background might be a performance win for us.
--
Jim C. Nasby, Data Architect jim(at)nasby(dot)net
512.569.9461 (cell) http://jim.nasby.net