[Xen-devel] about the funtion call memory_type_changed()

["Li, Liang Z" <liang.z.li@xxxxxxxxx>]

Hi Jan,

I found the restore process of the live migration is quit long, so I try to 
find out what's going on.
By debugging, I found the most time consuming process is restore the VM's MTRR 
MSR,
The process is done in the function hvm_load_mtrr_msr(), it will call the
memory_type_changed(), which eventually call the time consuming function
flush_all().

All this is caused by adding the memory_type_changed in your patch, here is the 
link
http://lists.xen.org/archives/html/xen-devel/2014-03/msg03792.html,

I am not sure if it's necessary to call flush_all, even it's necessary,  call 
the function
 hvm_load_mtrr_msr one time will cause dozens call of flush_all, and each call 
of the
 flush_all function will consume about 8 milliseconds, in my test environment, 
the VM
 has 4 VCPUs, the hvm_load_mtrr_msr() will be called four times, and totally 
consumes
 about 500 milliseconds. Obviously, there are too many flush_all calls.

 I think something should be done to solve this issue, do you think so?

Liang

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