Re: madvise (MADV_FREE)

[Christoph Rohland <hans-christoph.rohland@sap.com>]

Hi Chuck

Chuck Lever <cel@monkey.org> writes:

> ok, so you're asking for a lite(TM) version of DONTNEED that
> provides the following hint to the kernel: "i may be finished with
> this page, but i may also want to reuse it immediately."

I would say "... reuse this address space immediately and you can give
me _any_ data the next time". "Any data" means probably either the old
or a zero page.

That's the optimal strategy for the memory management modules of SAP
R/3.

> function 1 (could be MADV_DISCARD; currently MADV_DONTNEED):
>   discard pages.  if they are referenced again, the process causes page
>   faults to read original data (zero page for anonymous maps).

That would be also good.

> i'm interested to hear what big database folks have to say about this.

R/3 is not a database but probably the biggest database client. Often
much bigger than the database itself.

Greetings
		Christoph
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