Re: [PATCH v10 3/3] mm: add anonymous vma name refcounting

[Pavel Machek]

Hi!

> > I can understand that having a string can be quite beneficial e.g., when
> > dumping mmaps. If only user space knows the id <-> string mapping, that
> > can be quite tricky.
> >
> > However, I also do wonder if there would be a way to standardize/reserve
> > ids, such that a given id always corresponds to a specific user. If we
> > use an uint64_t for an id, there would be plenty room to reserve ids ...
> >
> > I'd really prefer if we can avoid using strings and instead using ids.
> 
> I wish it was that simple and for some names like [anon:.bss] or
> [anon:dalvik-zygote space] reserving a unique id would work, however
> some names like [anon:dalvik-/system/framework/boot-core-icu4j.art]
> are generated dynamically at runtime and include package name.

I'd be careful; if you allow special characters like that, you will
confuse some kind of parser.

> Packages are constantly evolving, new ones are developed, names can
> change, etc. So assigning a unique id for these names is not really
> feasible.
> That leaves us with the central facility option, which as I described
> in my previous email would be prohibitive from performance POV (IPC
> every time we have a new name or want to convert id to name).

That "central facility" option can be as simple as "mkdir
/somewhere/sanitized_id", using inode numbers for example. You don't
really need IPC.

Plus, I don't really believe the IPC cost would be prohibitive.

Or you could simply hash the string and use the hash as id...

Best regards,
								Pavel
-- 
http://www.livejournal.com/~pavelmachek

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