RE: [Xen-devel] [PATCH] permute with 2MB chunk

["Cui, Dexuan" <dexuan.cui@xxxxxxxxx>]

Hi Jean,
The patch does fix the bug. Great!

I made a test to change xc_hvm_build() to invoke 
xc_domain_memory_populate_physmap() in the same pfn order of that in the old 
permute(); then I created an HVM guest, and I met with almost the same slowness 
in it!
Looks the old poor version of permute() can incur high rate of cache miss, 
hence the slowness after S/R is caused?

However, I still have questions:
For the bug, I remember the slowness 
1) Only happens to HVM guest (PV-guest has not this issue);   -- any difference 
between HVM and PV here??
2) Only happens to S/R and local non-live migration, but doesn't happen to 
local live migration. -- any difference between live and non-live here??
And when we suffer from the slowness, "local live migrating" the HVM guest can 
make the performance back to normal!

Can you reproduce these in your side? If so, can you help to explain them? 

Many thanks!

-- Dexuan


-----Original Message-----
From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx 
[mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Jean Guyader
Sent: 2008年3月19日 2:03
To: xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-devel] [PATCH] permute with 2MB chunk


The memory permutation cause a slow down in case of a save/restore (bug 
1143). It works better when the mixing is done with 2MB chunks.

Signed-off-by: Jean Guyader <jean.guyader@xxxxxxxxxxxxx>

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