On 09/29/2009 05:50 PM, Lucas Meneghel Rodrigues wrote:
On Fri, 2009-09-25 at 05:22 -0400, Jiri Zupka wrote:
----- "Dor Laor"<dlaor@xxxxxxxxxx> wrote:
On 09/16/2009 04:09 PM, Jiri Zupka wrote:
----- "Dor Laor"<dlaor@xxxxxxxxxx> 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?
I think it can be done with some simple scripting and it will be fast
enough and more importantly, easier to understand and to change in the
future.
Here is a short example for creating lots of identical pages that
contain '0' apart for the last two bytes. If you'll run it in a single
guest you should expect to save lots of memory. Then you can change the
last bytes to random value and see the memory consumption grow:
[Remember to cancel the guest swap to keep it in the guest ram]
dd if=/dev/zero of=template count=1 bs=4094
echo '1' >> template
cp template large_file
for ((i=0;i<10;i++)) do dd if=large_file of=large_file conv=notrunc
oflag=append > /dev/null 2>&1 ; done
It creates a 4k*2^10 file with identical pages (since it's on tmpfs with
no swap)
Can you try it? It should be far simpler than the original option.
Thanks,
Dor
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