On Wed, 2005-11-02 at 02:43 +0100, Andrea Arcangeli wrote:
> On Tue, Nov 01, 2005 at 05:15:01PM -0800, Badari Pulavarty wrote:
> > Here is the patch to support madvise(MADV_FREE) - which frees
> > up the given range of pages and truncates the underlying backing
> > store. This basically provides "punch hole into file" functionality.
> > Currently it supports ONLY shmfs/tmpfs - where we have short term
> > need. Other filesystems return -ENOSYS.
>
> MADV_FREE as a name isn't right if we return -ENOSYS for anonymoys
> memory.
>
> MADV_FREE in other OS works _only_ on anonymous memory and returns
> -EINVAL if used on filebacked vmas. Infact we probably should rename our
> MADV_DONTNEED to MADV_FREE.
>
> http://docs.sun.com/app/docs/doc/816-5168/6mbb3hrde?a=view
>
> "This value cannot be used on mappings that have underlying file objects."
>
> Our MADV_DONTNEED exactly matches the MADV_FREE semantics, and it seems
> the MADV_DONTNEED of other OS isn't destructive like ours. Except our
> MADV_DONTNEED also works on filebacked mappings but it's destructive
> only on anonymous memory.
>
>
> I thought Andrew suggested MADV_REMOVE for the new feature.
Yep. My bad. Andrew did suggest MADV_REMOVE. Let me rename and
generate patch once again !! Thanks for pointing out.
>
> This feature didn't exist in other OS yet AFIK, so a new MADV_name for
> it makes sense. I'm not completely against extending MADV_FREE but then we
> shouldn't return -ENOSYS on anonymous memory and we should do the same
> thing MADV_DONTNEED does on anonymous memory. Probably a new name is
> safer to avoid confusion (think an application running MADV_FREE and
> expecting -EINVAL when used on filebacked mappings).
>
> Thanks!
>
Thanks,
Badari
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