Re: Problem with FreeBSD as a XenServer Guest - how to debug?

[Rainer Duffner]

> Am 04.02.2017 um 10:48 schrieb Florian Ermisch 
> :
> 
> Hi Rainer,
> 
> isn't Amazon AWS xen-based?
> I know Colin Percival (cperciva@) is running 
> tarsnap.com on AWS, maybe he knows how 
> to tune it properly?


It’s not a question of tuning.
It’s a factor of 5 that FreeBSD is slower. On SSDs, it’s 10 to 15x.


> Looks like he's the one providing FreeBSD 
> images for AWS, too: https://aws.amazon.com/marketplace/pp/B01LWSWRED/
> Amazon is probably running a heavily patched
> version of Xen but looking at the images' 
> sysctls & stuff and running one on your Xen-
> Server might provide some insights - or at
> least datapoints.
> 
> And then there's DTrace to dive into the 
> kernel's inner workings*…
> 


Yes, but I don’t even know there to start.
My knowledge of Dtrace is very, very limited.




> Oh, does Xen still provide emulation for other
> storage controllers like SATA or SAS? If so
> you may get an at least bearable performance
> using those.


FreeBSD 10 and 11 contain the „optimal“ support for Xen DomU support out-of-the 
box, AFAIK (the documentation / wiki for Xen is in a horrible state IMO).


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Re: Problem with FreeBSD as a XenServer Guest - how to debug?

[Florian Ermisch]

Hi Rainer,

isn't Amazon AWS xen-based?
I know Colin Percival (cperciva@) is running 
tarsnap.com on AWS, maybe he knows how 
to tune it properly?
Looks like he's the one providing FreeBSD 
images for AWS, too: https://aws.amazon.com/marketplace/pp/B01LWSWRED/
Amazon is probably running a heavily patched
version of Xen but looking at the images' 
sysctls & stuff and running one on your Xen-
Server might provide some insights - or at
least datapoints.

And then there's DTrace to dive into the 
kernel's inner workings*…

Oh, does Xen still provide emulation for other
storage controllers like SATA or SAS? If so
you may get an at least bearable performance
using those.

Regards, Florian

Am 4. Februar 2017 01:12:11 MEZ schrieb Rainer Duffner :
> Hi,
> 
> I’ve opened a PR on this:
> 
> https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=212681
> 
> and asked on freebsd-virtualization. But nothing came out of it.
> 
> Basically, I/O is very slow inside the FreeBSD guest. Linux guests are
> OK.
> FreeBSD 10 or 11 doesn’t make a difference.
> Haven’t been able to try 12.
> 
> 
> How can one debug this?
> 
> 
> 
> 
> Rainer
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Problem with FreeBSD as a XenServer Guest - how to debug?

[Rainer Duffner]

Hi,

I’ve opened a PR on this:

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=212681

and asked on freebsd-virtualization. But nothing came out of it.

Basically, I/O is very slow inside the FreeBSD guest. Linux guests are OK.
FreeBSD 10 or 11 doesn’t make a difference.
Haven’t been able to try 12.


How can one debug this?




Rainer
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