On Mon, 2007-10-15 at 17:26 -0500, Matt Mackall wrote:
> From: Matt Mackall <[email protected]>
>
> This makes physical page map counts available to userspace. Together
> with /proc/pid/pagemap and /proc/pid/clear_refs, this can be used to
> monitor memory usage on a per-page basis.
...
> + while (count > 0) {
> + ppage = pfn_to_page(pfn++);
> + if (!ppage)
> + pflags = 0;
> + else
> + pflags = ppage->flags;
> +
This one makes me worry a little bit. Are we sure that this won't
expose a wee bit too much to userspace?
I can see it making sense to clear the page refs, then inspect whether
the page has been referenced again. But, I worry that people are going
to start doing things like read NUMA, SPARSEMEM, or other internal
information out of these.
I've seen quite a few patches lately that do creative things with these
*cough*clameter*cough*, and I worry that they're too fluid to get
exposed to userspace.
Could we just have /proc/kpagereferenced? Is there a legitimate need
for other flags to be visible?
-- Dave
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