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

From: Michal Hocko <mhocko@suse.com>
To: Dave Hansen <dave.hansen@intel.com>
Cc: "Kees Cook" <keescook@chromium.org>,
	"Suren Baghdasaryan" <surenb@google.com>,
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Subject: Re: [PATCH v10 3/3] mm: add anonymous vma name refcounting
Date: Fri, 8 Oct 2021 16:57:32 +0200	[thread overview]
Message-ID: <YWBcXPZh9pYr0AHm@dhcp22.suse.cz> (raw)
In-Reply-To: <4a1dd04f-eda3-5c71-4772-726fd6fa2a38@intel.com>

On Fri 08-10-21 07:14:58, Dave Hansen wrote:
> On 10/7/21 11:34 PM, Michal Hocko wrote:
> >> Yes, please. It really seems like the folks that are interested in this
> >> feature want strings. (I certainly do.)
> > I am sorry but there were no strong arguments mentioned for strings so
> > far.
> 
> The folks who want this have maintained an out-of-tree patch using
> strings.  They've maintained it for the better part of a decade.  I
> don't know how widely this shipped in the Android ecosystem, but I
> suspect we're talking about billions of devices.  Right?
> 
> This is a feature that, if accepted into mainline, will get enabled and
> used on billions of devices.  If we dumb this down to integers, it's not
> 100% clear that it _will_ get used.
> 
> That's a pretty strong argument in my book, even if the contributors
> have difficulty articulating exactly why they want strings.

I would agree that if integers would make this unusable then this would
be a strong argument. But I haven't really heard any arguments like that
so far. I have heard about IPC overhead and other speculations that do
not seem really convincing. We shouldn't hand wave concerns regarding
the implementation complexity and resource handling just by "somebody
has been using this for decates", right?

Do not get me wrong. This is going to become a user interface and we
will have to maintain it for ever. As such an extra scrutiny has to be
applied.
-- 
Michal Hocko
SUSE Labs