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

On Tue, Jan 14, 2014 at 11:44 AM, James Bottomley
<James.Bottomley@hansenpartnership.com> wrote:
> No, I'm sorry, that's never going to be possible.  No user space
> application has all the facts.  If we give you an interface to force
> unconditional holding of dirty pages in core you'll livelock the system
> eventually because you made a wrong decision to hold too many dirty
> pages.   I don't understand why this has to be absolute: if you advise
> us to hold the pages dirty and we do up until it becomes a choice to
> hold on to the pages or to thrash the system into a livelock, why would
> you ever choose the latter?  And if, as I'm assuming, you never would,
> why don't you want the kernel to make that choice for you?

If you don't understand how write-ahead logging works, this
conversation is going nowhere.  Suffice it to say that the word
"ahead" is not optional.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company