Re: [RFC] Arch option to touch newly allocated pages

[Richard Gooch <rgooch@ras.ucalgary.ca>]

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David Woodhouse writes:
> 
> jdike@karaya.com said:
> >  Yeah, MADV_DONTNEED looks right.  UML and Linux/s390 (assuming VM has
> > the equivalent of MADV_DONTNEED) would need a hook in free_pages to
> > make that happen. 
> 
>        MADV_DONTNEED
>               Do  not expect access in the near future.  (For the
>               time being, the application is  finished  with  the
>               given range, so the kernel can free resources asso­
>               ciated with it.)
> 
> It's not clear from that that the host kernel is actually permitted to
> discard the data.
> 
> alan@lxorguk.ukuu.org.uk said:
> >  VM allows you to give it back a page and if you use it again you get
> > a clean copy. What it seems to lack is the more ideal "here have this
> > page and if I reuse it trap if you did throw it out" semantic. 
> 
> I've wittered on occasion about other situations where such
> semantics might be useful -- essentially 'drop these pages if you
> need to as if they were clean, and tell me when I next touch them so
> I can recreate their data'.

Indeed. I'd love such a feature. It's got applications in
numerical/scientific code, not just UML.

				Regards,

					Richard....
Permanent: rgooch@atnf.csiro.au
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