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Date: Tue, 19 Jan 2010 10:07:07 +0200
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Subject: Re: [PATCH v6] add MAP_UNLOCKED mmap flag
From: Pekka Enberg <penberg@cs.helsinki.fi>
To: Gleb Natapov <gleb@redhat.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>, linux-mm@kvack.org,
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       "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
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Hi Gleb,

On Tue, Jan 19, 2010 at 9:52 AM, Gleb Natapov <gleb@redhat.com> wrote:
>> It would be probably useful if you could point us to the application
>> source code that actually wants this feature.
>>
> This is two line patch to qemu that calls mlockall(MCL_CURRENT|MCL_FUTURE)
> at the beginning of the main() and changes guest memory allocation to
> use MAP_UNLOCKED flag. All alternative solutions in this thread suggest
> that I should rewrite qemu + all library it uses. You see why I can't
> take them seriously?

Well, that's not going to be portable, is it, so the application
design would still be broken, no? Did you try using (or extending)
posix_madvise(MADV_DONTNEED) for the guest address space? It seems to
me that you're trying to use a big hammer (mlock) when a polite hint
for the VM would probably be sufficient for it do its job.

                        Pekka