Re: [Xen-users] Serious performance problems - is Xen not ready for production use?

[Xuehai Zhang <hai@xxxxxxxxxxxxxxx>]

On Thu, 14 Jul 2005, Mark Williamson wrote:

> <snip>
>
> > When I had a closer look to the mem line:
> > Mem:    257488K total,   255368K used,     2120K free,      128K buffers
> >
> > ...it looked strange to me. I checked and found my config file for this
> > domain looking like this:
> >
> > ...
> > memory = 128
> > extra = "mem=268435456"
> > ...
>
> Well spotted!
>
> > This was left over from my tries to get the "xm balloon" working. I
> > removed the extra line from the config file - and voila, it works... Is
> > this config above wrong at all or is the strange behaviour I found
> > related to the bugs with balloon feature..?
>
> The config line looks OK at first glance but...  I wonder what units the mem
> parameter expects: if it expects KB then you've just caused it to allocate a
> frame table for an absolutely *huge* physical memory, which would account for
> all the real memory being allocated.

My experiment shows changing "mem=268435456" to "mem=256m" doesn't
help with the ballooning above initial allocation problem.
(Linux BootPrompt-Howto
(http://en.tldp.org/HOWTO/BootPrompt-HOWTO-3.html#ss3.3)
suggests both "k" and "m" suffixes can be used for "mem=" argument).

BTW, i still think "mem=268435456" is a valid configuration to give memory
in bytes. Both "dmesg" and "free" outputs form the domain booted with this
configuration show the domain is booted with 256MB memory.


> I can't guess any better without going through the code - it should hopefully
> become apparent when someone fixes the ballooning problem (does anyone want
> to volunteer for that, btw?  It'd be useful if someone could post a patch.).
>
> Cheers,
> Mark
>
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>
>

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