Re: [RFC][PATCH 0/6] Critical Page Pool

[Sridhar Samudrala <sri@us.ibm.com>]

Matthew Dobson wrote:

>Pavel Machek wrote:
>  
>
>>>>And as you noticed, it does not work for your original usage case,
>>>>because reserved memory pool would have to be "sum of all network
>>>>interface bandwidths * ammount of time expected to survive without
>>>>network" which is way too much.
>>>>        
>>>>
>>>Well, I never suggested it didn't work for my original usage case.  The
>>>discussion we had is that it would be incredibly difficult to 100%
>>>iron-clad guarantee that the pool would NEVER run out of pages.  But we can
>>>size the pool, especially given a decent workload approximation, so as to
>>>make failure far less likely.
>>>      
>>>
>>Perhaps you should add file in Documentation/ explaining it is not
>>reliable?
>>    
>>
>
>That's a good suggestion.  I will rework the patch's additions to
>Documentation/sysctl/vm.txt to be more clear about exactly what we're
>providing.
>
>
>  
>
>>>>If you want few emergency pages for some strange hack you are doing
>>>>(swapping over network?), just put swap into ramdisk and swapon() it
>>>>when you are in emergency, or use memory hotplug and plug few more
>>>>gigabytes into your machine. But don't go introducing infrastructure
>>>>that _can't_ be used right.
>>>>        
>>>>
>>>Well, that's basically the point of posting these patches as an RFC.  I'm
>>>not quite so delusional as to think they're going to get picked up right
>>>now.  I was, however, hoping for feedback to figure out how to design
>>>infrastructure that *can* be used right, as well as trying to find other
>>>potential users of such a feature.
>>>      
>>>
>>Well, we don't usually take infrastructure that has no in-kernel
>>users, and example user would indeed be nice.
>>							Pavel
>>    
>>
>
>Understood.  I certainly wouldn't expect otherwise.  I'll see if I can get
>Sridhar to post his networking changes that take advantage of this.
>  
>
I have posted these patches yesterday on lkml and netdev and here is a 
link to the thread.
    http://thread.gmane.org/gmane.linux.kernel/357835
  
Thanks
Sridhar