RE: [Xen-ia64-devel] [PATCH] [RESEND] domU destroy & page ref counter

["Magenheimer, Dan (HP Labs Fort Collins)" <dan.magenheimer@xxxxxx>]

Rid mangling change has been discussed many times on the list,
most recently:

http://lists.xensource.com/archives/html/xen-ia64-devel/2005-11/msg00282.html 

> -----Original Message-----
> From: xen-ia64-devel-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-ia64-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf 
> Of Xu, Anthony
> Sent: Monday, March 13, 2006 6:37 PM
> To: Dong, Eddie; Tian, Kevin; Akio Takebe; Masaki Kanno; 
> xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
> Subject: RE: [Xen-ia64-devel] [PATCH] [RESEND] domU destroy & 
> page ref counter
> 
> >From: Dong, Eddie
> >Sent: 2006年3月13日 22:12
> >A minor suggestion for next in my mind is that we may add a 
> simple COMPILE option
> >in Makefile or some .h file to be able to choice 1/3 byte 
> swap or 1/2 byte swap.
> >People has some thoughts that 1/2 byte swap may have better 
> hash locality.
> >
> >Eddie.
> I second Eddie,
> 
> I have some observations about this.
> Usually guest applications use almost the address space, the 
> only different is 
> rid. What I observed was if the lowest 17 bits of rid are 
> same, the hash address 
> is same. If we swap 1/3 byte, applications use the same 
> address space but different 
> rid may have the hash address in a majority of situations, 
> which may make some 
> collision chains very long.
> 
> These are just some observations, I don't mean 1/2 byte swap 
> is better than 1/3 
> byte swap.I think we need to add COMPILE option to get 
> benchmark data first, and 
> then make the decision.
> 
> It's obviously not a big task but deserve to do. One thing we 
> need to pay extra
> attention is the rid byte swap is done in assembly code in 
> some fast_hyperpriops.
> 
> Thanks,
> Anthony
> 
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