Re: madvise (MADV_FREE)

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

Jamie Lokier <jamie.lokier@cern.ch> writes:
> Christoph Rohland wrote:
> > > 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.
> 
> For maximum performance that's right.  But Linux normally has to
> provide some minimal security, so an application should only see its
> own data or zeros, not an arbitrary page.

That was the reason for "...probably either the old or a zero page"

> Zeroing has another advantage: you can efficiently detect it.  So
> you can use it for cached memory objects too in a number of cases,
> not just free memory.  (A bit from mincore would also allow
> detection, but not nearly as efficiently).
> 
> > That's the optimal strategy for the memory management modules of
> > SAP R/3.
> 
> Excellent!  A hard core recommendation :-)

:-)

Greetings
		Christoph
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