Re: [-mm PATCH] Memory controller improve user interface

[Dave Hansen]

On Thu, 2007-08-30 at 03:57 +0530, Balbir Singh wrote:
> True, mmap() is a good example of such an interface for developers, I
> am not sure about system admins though.
> 
> To quote Andrew
> <quote>
> Reporting tools could run getpagesize() and do the arithmetic, but we
> generally try to avoid exposing PAGE_SIZE, HZ, etc to userspace in this
> manner.
> </quote>

Well, rounding to PAGE_SIZE exposes PAGE_SIZE as well, just in a
non-intuitive fashion. :)

If we're going to modify what the user specifies, we should probably at
least mandate that writes are only a "suggestion" and users must read
back the value to ensure what actually got committed.

If we're going to round in any direction, shouldn't we round up?  If a
user specifies 4097 bytes and uses two pages, we don't want to complain
when they hit that second page.  

-- Dave

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