Re: [PATCH v9 2/3] mm: add a field to store names for private anonymous memory

[Suren Baghdasaryan]

On Sun, Sep 5, 2021 at 6:04 AM Pavel Machek <pavel@xxxxxx> wrote:
>
> Hi!
>
> > > the process is still running, so it has to have some sort of
> > > synchronization with every layer of userspace.  Efficiently tracking
> > > the ranges requires reimplementing something like the kernel vma
> > > trees, and linking to it from every layer of userspace.  It requires
> > > more memory, more syscalls, more runtime cost, and more complexity to
> > > separately track regions that the kernel is already tracking.
>
> Ok so far.
>
> > > This patch adds a field to /proc/pid/maps and /proc/pid/smaps to show a
> > > userspace-provided name for anonymous vmas.  The names of named anonymous
> > > vmas are shown in /proc/pid/maps and /proc/pid/smaps as [anon:<name>].
> > >
> > > Userspace can set the name for a region of memory by calling
> > > prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, start, len, (unsigned
> > > long)name);
>
> Would setting a 64-bit integer instead of name be enough? Even if
> each party would set it randomly, risk of collisions would be very
> low... and we'd not have to deal with strings in kernel.

Thanks for the question, Pavel. I believe this was discussed in this
thread before and Colin provided the explanation with usage examples:
https://lore.kernel.org/linux-mm/20200821070552.GW2074@grain/.
Thanks,
Suren.

>
>                                                                 Pavel
>
>
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