RE: [Xen-devel] Xenoprof in an HVM domain - Yang, Xiaowei - com.xensource.lists.xen-devel

12 messages in com.xensource.lists.xen-develRE: [Xen-devel] Xenoprof in an HVM do...

From	Sent On	Attachments
Steve Dobbelstein	21 Apr 2006 13:10
Yang, Xiaowei	24 Apr 2006 00:02
Steve Dobbelstein	24 Apr 2006 13:08
Santos, Jose Renato G	24 Apr 2006 13:27
Ray Bryant	25 May 2006 07:20
Santos, Jose Renato G	25 May 2006 09:43
Ray Bryant	25 May 2006 11:38
Santos, Jose Renato G	25 May 2006 14:44
Ray Bryant	25 May 2006 15:01
Santos, Jose Renato G	26 May 2006 09:55
Stephane Eranian	30 May 2006 04:58
Santos, Jose Renato G	30 May 2006 19:09

Subject:	RE: [Xen-devel] Xenoprof in an HVM domain
From:	Yang, Xiaowei (xiao...@intel.com)
Date:	04/24/2006 12:02:18 AM
List:	com.xensource.lists.xen-devel

Hi Steve,

As we know, xenoprof 2.0 is checked in xen-unstable for days. Now I'm writing a
patch to add passive domain support (which exists in UP guest age) for smp
guest. Using passive domain and my improvement in oprofile (I sent out before),
we needn't change guest code and can tune hvm guest in a somewhat raw way -- PC
samples from hv and guest kernel can be mapped to functions but all samples from
application are only there as a whole. It's enough for tuning hvm performace for
now. You are proposing to add active domain support for hvm, right? The apparent
advantage is to tune hvm linux applications in future. It should be doable, like
we've enabled vbd/vnif in hvm. And it needs more effort in hvm. Yes, Hypervcall, shared buffer and notification mechanism are all needed. For
the last one, one of simple way is: 1) in hvm guest kernel, register for an
unused IRQ line 2) in hv, inject that interrupt to hvm when needed. Or you can
use a psydo PCI device in qemu to hold one irq number.

Thanks, -Xiaowei

-----Original Message----- From: xen-...@lists.xensource.com
[mailto:xen-...@lists.xensource.com] On Behalf Of Steve Dobbelstein Sent: 2006年4月21日 13:11 To: xen-...@lists.xensource.com Subject: [Xen-devel] Xenoprof in an HVM domain

I'm looking into getting Xenoprof to tun in an HVM domain, since we will eventually need a profiler for HVM domains to track down areas of poor performance. (HVMs have poor performance? :) ) Being relatively new to OProfile, Xenoprof, and Xen internals, I would appreciate any pointers, tips, and comments on how to work the implementation. I see three basic areas of work.

1. Implement hypercalls in HVM domains. This has been done by Steve Ofsthun of Virtual Iron who contributed his patches to the xen-devel list recently. (Thanks, Steve.)

2. Implement the shared buffer that conveys profile events from the hypervisor to the domain. From my initial crawl through the Xenoprof code (see for example linux-2.6-xen-sparse/arch/i386/oprofile/xenoprof.c) it appears that its setup of the shared buffer via hypercalls and page table updates should work in an HVM domain. Correct me if I'm wrong.

3. Implement an interrupt mechanism for the hypervisor to signal the domain that it has more data in the shared buffer. Xenoprof currently sets up an event channel for this. In my initial hack of the code I discovered that the event channel used by Xenoprof conflicts with the 8259 support in the HVM kernel. Since I use the serial interface to the HVM domain, I am hesitant to remove the 8259 support in my HVM kernel. It appears that I need to either get an event channel to work through qemu, preserving the 8259 functionality, or change Xenoprof in the hypervisor to instruct qemu to issue an interrupt to the domain and change Xenoprof in the domain to run off an interrupt instead of an event channel. Or maybe I don't know what I'm talking about and need to be enlightened by those who know better what the issues are.

Any advice is appreciated.

Thanks, Steve D.