Re: [KVM-AUTOTEST PATCH 1/2] Add KSM test

[Lucas Meneghel Rodrigues <lmr@redhat.com>]

On Fri, 2009-09-25 at 05:22 -0400, Jiri Zupka wrote:
> ----- "Dor Laor" <dlaor@redhat.com> wrote:
> 
> > On 09/16/2009 04:09 PM, Jiri Zupka wrote:
> > >
> > > ----- "Dor Laor"<dlaor@redhat.com>  wrote:
> > >
> > >> On 09/15/2009 09:58 PM, Jiri Zupka wrote:
> > >>>> After a quick review I have the following questions:
> > >>>> 1. Why did you implement the guest tool in 'c' and not in
> > python?
> > >>>>     Python is much simpler and you can share some code with the
> > >> server.
> > >>>>     This 'test protocol' would also be easier to understand this
> > >> way.
> > >>>
> > >>> We need speed and the precise control of allocate memory in
> > pages.
> > >>>
> > >>>> 2. IMHO there is no need to use select, you can do blocking
> > read.
> > >>>
> > >>> We replace socket communication by interactive program
> > communication
> > >> via ssh/telnet
> > >>>
> > >>>> 3. Also you can use plain malloc without the more complex ( a
> > bit)
> > >> mmap.
> > >>>
> > >>> We need address exactly the memory pages. We can't allow shift of
> > >> the data in memory.
> > >>
> > >> You can use the tmpfs+dd idea instead of the specific program as I
> > >> detailed before. Maybe some other binary can be used. My intention
> > is
> > >> to
> > >> simplify the test/environment as much as possible.
> > >>
> > >
> > > We need compatibility with others system, like Windows etc..
> > > We want to add support for others system in next version
> > 
> > KSM is a host feature and should be agnostic to the guest.
> > Also I don't think your code will compile on windows...
> 
> Yes, I think you have true. 

First of all, sorry, I am doing the best I can to review carefully all
the patch queue, and as KSM is a more involved feature that I am not
very familiar with, I need a bit more time to review it!

> But because we need generate special data to pages in memory. 
> We need use script on guest side of test. Because communication 
> over ssh is to slow to transfer lot of GB of special data to guests.
> 
> We can use optimized C program which is 10x and more faster than 
> python script on native system. Heavy load of virtual guest can 
> make some performance problem.

About code compiling under windows, I guess making a native windows c or
c++ program is an option, I generally agree with your reasoning, this
case seems to be better covered with a c program. Will get into it in
more detail ASAP...

> We can use tmpfs but with python script to generate special data. 
> We can't use dd with random because we need test some special case.
> (change only last 96B of page etc.. )
> 
> 
> What do you think about it? 
> 
> > 
> > >
> > >>
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