[ENBD] Anyone got swapping over NBD-2.4.25 working?

[Alan Messer]

Jason A. Pattie wrote:

> I have had similar experiences, except it didn't last as long as you 
> were able to get it to work.  The explanation I got from PTB was the 
> fact that each child thread (being in userspace) requires a specific 
> amount of memory in order to run.  Well, if a child thread is "swapped 
> out", but it needs to be resurrected to do some work, but there isn't 
> enough memory to pull it back and if all the other child processes have 
> been "swapped out", then ... well, you see the quandry.  (It's something 
> like that)


Indeed. I suspected this might be the problem. Did you try any of 
the old patches to overcome this problem? Aren't there any options 
in Linux to 'pin down' (make unswappable) certain memory regions? 
Perhaps this would help for critical sections? Of course,  code 
canbe swapped too, which might be more of a problem.

 
> You can increase the number of child processes that get spawned, but you 
> will just be staving off the inevitable.


Interesting. If I understand correctly, the kernel is quite happy, 
but the swap action gets stuck. Therefore, other swaps and 
processes can continue to run? I'll try a few more processes to 
see if this is true.

Alan.