Re: [PATCH v6] add MAP_UNLOCKED mmap flag

From: Pekka Enberg
Date: Tue Jan 19 2010 - 03:07:22 EST

Hi Gleb,

On Tue, Jan 19, 2010 at 9:52 AM, Gleb Natapov <gleb@xxxxxxxxxx> 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.

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