Re: [Xen-users] how to use tmem function with xl command

[Luca Lesinigo <luca@xxxxxxxxx>]

Il giorno 01/mar/2012, alle ore 04:33, hxkhust ha scritto:
> Where could find some documentation about the following features which xl 
> command has ?I have read some papers about tmem and try to use it,but I don't 
> know how to use the tmem interface that xl command provide.Does anybody can 
> help me?
You don't need to run any xm/xl command to use tmem.

Tmem will be provided by the hypervisor to guests simply adding the 'tmem' 
option to its command line (and you'll probably want tmem_dedup and 
tmem_compress too, refer to the docs to know if they are a good or bad choice 
for you). You can check if it has been actually enabled by looking at the 
hypervisor's dmesg for a line like this:
        (XEN) tmem: initialized comp=1 dedup=1 tze=0 global-lock=0 

Guest usage of tmem is actually specific to the guest. Recent linux kernels, 
for example, have cleancache already integrated and that'll be the most usual 
use case right now. On those kernels, you can enable tmem support by adding 
"tmem" to the linux kernel command line, and the cleancache driver will 
automatically use that. You can check it out by looking at the linux kernel's 
dmesg for a line like this:
        cleancache enabled, RAM provided by Xen Transcendent Memory 

Please note that only recent (>= linux-3.0, IIRC) linux kernels have cleancache 
merged in, unless you manually patch it in.

--
Luca Lesinigo
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