Re: manual page migration -- issue list

[Ray Bryant <raybry@sgi.com>]

Paul Jackson wrote:
> A couple comments in response to Andi's earlier post on the
> related lkml thread ...
> 
> Andi wrote:
> 
>>Sorry, but the only real difference between your API and mbind is that
>>yours has a pid argument. 
> 
> 
> One other difference shouts out at me.  I am unsure of my reading of
> Andi's post, so I can't tell if (1) it was so obvious Andi didn't
> bother mentioning it, or (2) he doesn't see it as a difference.
> 
> That difference is this.
> 
>     The various numa mechanisms, such as mbind, set_mempolicy and cpusets,
>     as well as the simple first touch that MPI jobs rely on, are all about
>     setting a policy for where future allocations should go.
> 
>     This page migration mechanism is all about changing the placement of
>     physical pages of ram that are currently allocated.
> 
> At any point in time, numa policy guides future allocations, and page
> migration redoes past allocations.
> 

Very nicely said, thanks.  And the concern I have been trying to raise with
Andi is:

       How does that page migration mechanism redo a past allocation using
       a memory policy if the orginal allocation was not done with a memory
       policy, but instead done via first touch?

> 
> Andi wrote:
> 
>>My thinking is the simplest way to handle that is to have a call that just
>>migrates everything. 
> 
> 
> I might have ended up at the same place, not sure, when I just suggested
> in my previous post:
> 
> pj wrote:
> 
>>As a straw man, let me push the factored migration call to the
>>extreme, and propose a call:
>>
>>  sys_page_migrate(pid, oldnode, newnode)
>>
>>that moves any physical page in the address space of pid that is
>>currently located on oldnode to newnode.
> 
> 
> 


-- 
-----------------------------------------------
Ray Bryant
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raybry@sgi.com             raybry@austin.rr.com
The box said: "Requires Windows 98 or better",
	 so I installed Linux.
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