Behavior of madvise(MADV_FREE)

[Poul-Henning Kamp]

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In message <50786023.1000206 at rice.edu>, Alan Cox writes:

>Given the way that madvise(MADV_FREE) is still used by malloc()/free(), 
>any additional overhead would still be a pessimization most of the 
>time.

That would be my fear too.

>Over the years, I think you and I have both said that what we 
>really need is the ability for the kernel to deliver an event to 
>malloc()/free() when memory is trending toward scarcity.

I still think this would be a good idea, and I can only assume that
the absense of this feature is due to Jason Evans failing in his
malloc-maintainers duty of bugging the VM people for this feature
at every conceiveable opportunity :-)

That being said, my experience with Varnish does indicate that intelligent
use of VM from userland is close to a lost case, in no small part because
of the lack of a good API.

If you can spare a student of sufficient quality, it might be a good assignment
to design a new VM-API, relative to the current reality of things like
malware attacks, "no-execute" bits etc.


-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
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Never attribute to malice what can adequately be explained by incompetence.