Re: [RFC, PATCH 0/8] remap_file_pages() decommission

[Peter Zijlstra <peterz@infradead.org>]

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On Tue, May 06, 2014 at 04:28:56PM -0700, Andrew Morton wrote:
> On Wed, 7 May 2014 02:03:23 +0300 "Kirill A. Shutemov" <kirill@shutemov.name> wrote:
> 
> > remap_file_pages(2) was invented to be able efficiently map parts of
> > huge file into limited 32-bit virtual address space such as in database
> > workloads.
> > 
> > Nonlinear mappings are pain to support and it seems there's no
> > legitimate use-cases nowadays since 64-bit systems are widely available.
> > 
> > Let's deprecate remap_file_pages() syscall in hope to get rid of code
> > one day.
> 
> Before we do this we should ensure that your proposed replacement is viable
> and desirable.  If we later decide not to proceed with it, this patch will
> sow confusion.

Chicken meet Egg ?

How are we supposed to test if its viable if we have no known users? The
printk() might maybe (hopefully) get us some reaction in say a years
time, much longer if we're really unlucky.

That said, we could make the syscall return -ENOSYS unless a sysctl was
touched. The printk() would indeed have to mention said sysctl and a
place to find information about why we're doing this..

But by creating more pain (people have to actually set the sysctl, and
we'll have to universally agree to inflict pain on distro people that
set it by default -- say, starve them from beer at the next conf.) we're
more likely to get an answer sooner.



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