RE: [Xen-devel] [PATCH] linux/balloon: don't allow ballooningdowna domain below a reasonable limit - Dan Magenheimer - com.xensource.lists.xen-devel

25 messages in com.xensource.lists.xen-develRE: [Xen-devel] [PATCH] linux/balloon...

From	Sent On	Attachments
Jan Beulich	04 Apr 2008 08:07
Keir Fraser	05 Apr 2008 14:39
Jan Beulich	07 Apr 2008 00:09
Dan Magenheimer	29 Apr 2008 11:34
Jan Beulich	29 Apr 2008 23:28
Dan Magenheimer	30 Apr 2008 09:03
Dan Magenheimer	30 Apr 2008 16:49
Keir Fraser	01 May 2008 00:01
Dan Magenheimer	01 May 2008 07:44
Alan Cox	01 May 2008 09:36
Keir Fraser	01 May 2008 09:55
Dan Magenheimer	01 May 2008 09:59
Alan Cox	01 May 2008 13:04
Keir Fraser	01 May 2008 14:18
Alan Cox	01 May 2008 16:02
Dan Magenheimer	01 May 2008 16:27
Keir Fraser	02 May 2008 00:04
Dan Magenheimer	03 May 2008 06:53
Keir Fraser	03 May 2008 07:11
Mark Williamson	03 May 2008 10:31
Dan Magenheimer	03 May 2008 12:27
Dan Magenheimer	03 May 2008 12:42
Ian Pratt	12 May 2008 15:19
Dan Magenheimer	12 May 2008 16:34
Markus Hochholdinger	13 May 2008 03:35

Subject:	RE: [Xen-devel] [PATCH] linux/balloon: don't allow ballooningdowna domain below a reasonable limit
From:	Dan Magenheimer (dan....@oracle.com)
Date:	04/30/2008 09:03:42 AM
List:	com.xensource.lists.xen-devel

Hi Jan --

Thanks for the reply. I see the comment now... it didn't find its way into the source.

I will definitely be working on tuning this estimate as I am working on maximizing the number of domains that can be run on a system and this is a constraint. As a quick-and-dirty test, I just divided the result of your algorithm (on a 512MB domain) by two and the maximally-ballooned kernel still ran fine (with 86528kB instead of 173056kB).

Could you explain the logic behind your current algorithm? I understand you are trying to estimate the additional kernel data structure space with the addition of the max_pfn computation but don't understand why this is a good estimator. I also am wondering how you chose the magic values for x in MB2PAGES(x). And also if you have any tests/workloads you might have used to evaluate the algorithm.

Thanks, Dan

-----Original Message----- From: Jan Beulich [mailto:jbeu...@novell.com] Sent: Wednesday, April 30, 2008 12:29 AM To: dan....@oracle.com Cc: Keir Fraser; xen-...@lists.xensource.com; Ky Srinivasan; KurtGarloff Subject: RE: [Xen-devel] [PATCH] linux/balloon: don't allow ballooningdowna domain below a reasonable limit

"Dan Magenheimer" <dan....@oracle.com> 29.04.08 20:35 >>>

I made some actual measurements of the results of this algorithm (on a RHEL5u1-32bit guest).

memory= Minimum 128 75776kB 256 108544kB 512 173056kB 1024 238592kB

This corresponds to expected values in the source comment However, I wonder if the algorithm is probably too conservative for large(r) memory domains. With a light load (i.e. continuously compiling Xen), memory utilization rarely exceeds 72MB, regardless of the max memory (at least in the above tested values).

Sure, this was (in different wording) also stated in the comment that came with the patch. A more precise estimate would certainly be welcome, but I'm afraid is going to come with a much higher (complexity) price tag. Unless you have something simple and obvious in mind that we simply didn't spot...