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From: Brian Geffon <bgeffon@google.com>
To: "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>
Cc: linux-man@vger.kernel.org, Sonny Rao <sonnyrao@google.com>,
	Jesse Barnes <jsbarnes@google.com>,
	Vlastimil Babka <vbabka@suse.cz>,
	Minchan Kim <minchan@kernel.org>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Lokesh Gidra <lokeshgidra@google.com>
Subject: Re: [PATCH v2] mremap.2: Add information for MREMAP_DONTUNMAP.
Date: Thu, 16 Apr 2020 20:01:49 -0700	[thread overview]
Message-ID: <CADyq12xA69pSZ=JfMuG_c8T1UHepmdSqBwLLPgFrOyXeveVk4w@mail.gmail.com> (raw)
In-Reply-To: <092fc948-4adb-cda8-f525-7d16a85674e7@gmail.com>

Hi Michael,

> Thanks for this patch. I've applied it, and done quite a
> bit of editing. Could you please take a look at the
> version in Git, and let me know if I made any bad changes
> to your text.

Your changes look good.

> You write "move", but would it not be more correcrt to say something
> like "duplicate"?

It's a little of both, it duplicates the VMA but moves the page table
entries. So the behavior feels more like a move followed by a new
mapping created that had the same properties as the previous. Does
that make sense?

> > +Possible applications for this behavior might be garbage collection or
>
> Can you elaborate the garbage collection use case a little, please?

Lokesh, who is CCed, can probably expand better than I can, Lokesh
would you mind elaborating on how the JVM plans to use this.

> > +non-cooperative
> > +.BR userfaultfd (2) .
>
> What is noncooperative userfaultfd(2)?

No cooperative userfaultfd is the term that people tend to use when
the threads accessing the memory are not cooperating with the fault
handling, MREMAP_DONTUNMAP is interesting for this as you can yank out
the page tables from a running process and immediately start handling
faults for the registered range without having to stop the process.

I hope that answers your questions, feel free to ask if you need more
clarification.

Brian

  reply	other threads:[~2020-04-17  3:02 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-15 16:49 [PATCH v2] mremap.2: Add information for MREMAP_DONTUNMAP Brian Geffon
2020-04-16  7:07 ` Michael Kerrisk (man-pages)
2020-04-17  3:01   ` Brian Geffon [this message]
2020-04-22  0:15     ` Lokesh Gidra
2020-04-22 12:08       ` Michael Kerrisk (man-pages)
2020-04-22 12:05     ` Michael Kerrisk (man-pages)

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