[Lse-tech] Minutes from 4/5 Con Call

[Hanna L. <ha...@us...>]

		LSE Con Call Minutes April 5

Daniel Phillips-  Discontiguous Memory 

	Daniel creates a new logical address space controlled by
a nonlinear config option. This gets away from the one-to-one mapping
between physical and virtual memory.
	This patch gets rid of __pa(*) and __va(*) and replaces 
them with uniform physical to virtual and virtual to physical. They 
are all inlines instead of macros.
	A patch exists and it boots under UML. It should be 
out for RFC in a few days. The part of it that changes header 
files has already been sent out for RFC and it was well received.
Here is a link to that posting:
http://marc.theaimsgroup.com/?l=linux-kernel&m=101718877223347&w=2
	He hasn't tried to do intelligent NUMA allocation yet. 
This patch doesn't have a concept of nodes now. How to make it 
work best with NUMA is still an open question.
	Kanoj examined Dan's approach fairly aggressivly 
especially with regard to TLB and cacheline utilization. Dan was 
able to convince him it was the right way over the course of 
dinner. 

Martin Bligh - NUMA kernel text replication

	Tony Luck has already done this for ia64 but he had 
hardware support that ia32 doesn't. If you have multiple copies 
of kernel code need to make sure the running kernel thread can 
point to the right kernel text. 
	They went into details of how DYNIX/ptx dealt with
this problem on their NUMA-Q hardware. They did strange 
things with L1 and L2 caches among other things.
	Daniel said some of this might go along nicely 
with his non linear stuff. 
	We want to avoid a global kmap table and go for 
a per process or per task kmap table. Currently can't even 
boot with 64 gig memory because it will run out of kva 
structs. Even 32 gb is pretty tight. 
	Daniel suggested use 1 struct page for every 16 k 
instead of every 4k. Martin said that is what they call 
page clustering. Then a long talk ensued between 
Daniel/Martin/Dave McCracken.  Toward the end Daniel said the 
page clusters stuff is going to be needed either way he won't
have time to work on it soon.  Dave said he might start looking
into it.

Hanna Linder - 

	Please somebody volunteer to take minutes at the
next meeting April 19th.

minutes compiled by a ha...@us...