Re: [PATCH v6] add MAP_UNLOCKED mmap flag

From: Pekka Enberg
Date: Tue Jan 19 2010 - 03:44:31 EST

Hi Gleb,

On Tue, Jan 19, 2010 at 10:26 AM, Gleb Natapov <gleb@xxxxxxxxxx> wrote:
>> design would still be broken, no? Did you try using (or extending)
>> posix_madvise(MADV_DONTNEED) for the guest address space? It seems to
> After mlockall() I can't even allocate guest address space. Or do you mean
> instead of mlockall()? Then how MADV_DONTNEED will help? It just drops
> page table for the address range (which is not what I need) and does not
> have any long time effect.

Oh right, MADV_DONTNEED is no good.

On Tue, Jan 19, 2010 at 10:26 AM, Gleb Natapov <gleb@xxxxxxxxxx> wrote:
>> 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.
> I what to tell to VM "swap this, don't swap that" and as far as I see
> there is no other way to do it currently.

Yeah, which is why I was suggesting that maybe posix_madvise() needs
to be extended to have a MADV_NEED_BUT_LESS_IMPORTANT flag that can be
used as a hint by mm/vmscan.c to first swap the guest address spaces.

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