Re: Regression: Requiring CAP_SYS_ADMIN for /proc/<pid>/pagemap causes application-level breakage

[Mark Williamson]

>> Something like this (see patch in attachment)
>
> THP is not covered.
>
> Any comments on kcmp() idea?

It seems like a modified kcmp() would also be a valid approach but, as
you noted, probably speed-limited for our purposes.  As you say, there
is the option of a vector-oriented equivalent.  It seems like a
generally nice facility to have available in the kernel but my
suspicion is that it wouldn't be optimal for us...

My thinking is that using soft-dirty might give us the best
performance on platforms where it's available.  We're only using
fork() as a cunning/hacky way of tracking what pages change;
soft-dirty would allow us to avoid that too, whereas using kcmp()
would still require the forking overhead.

Does that make sense, or have I missed something?

Thanks,
Mark
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