Re: [Xen-devel] Xen GCOV Patches for latest Xen Unbstable and linux 2.6.18.8 kernel(32/64bit)

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Sat, May 08, 2010 at 01:31:01AM +0530, Tej wrote:
> All,
> 
> Here are the latest patches to expreiment with gcov profiler for xen
> hypervisor. I have tested current patches on Intel i686.

Nice..

> System Details:
> gcc version 4.3.3 (Ubuntu 4.3.3-5ubuntu4)
> gcov (Ubuntu 4.3.3-5ubuntu4) 4.3.3
> Kernel 2.6.28-11-generic

Uhh? 2.6.28 or 2.6.18?

I hate to tell you this but development is happening in the pv-ops
kernel, not anymore in the XenLinux branches :-(

Any chance you can rebase those patches against the pv-ops kernel?

Looking briefly at the Linux patches, you need to remove those #ifdef
LINUX_VERSION_CODE, make the EXPORT_SYMBOL be EXPORT_SYMBOL_GPL, and
also run the patch through scripts/checkpatch.pl
> Distribution: Ubuntu jaunty 9.04
> 
> There are some design issue which i would like to highlight here:
> 1. To create gcov proc dir user /proc/xen, we are explicitly exported
> xen_base symbol. I want to know your thoughts.
> 2. XEN_GCOV_PROC config is set as not selected. So someone has to be
> configured manually as M/Y
> 
> 
> Known Issues:
> File vmac.c throw some fault while using with lcov/gcov. This is due
> to some raw count copy between xen and kernel. I could not able to
> reproduce it many times, may be someone can try on 64 bit m/c.
> "My take on this is that zero length array element in gcov_info
> structure has to be copied separately between xen and kernel. How? I
> dont know."
> 
> I am still debugging this issue.
> 
> If you get fault and fail to proceed please apply the above patch in
> linux-wa-v1.patch in Linux 2.6.18.8 and recompile. This time vmac.gcda
> file wont appear in /proc/xen/gcov/crypto
> 
> 
> HOWTO Test using lcov
> 1.  install lcov from repo
>      # sudo apt-get install lcov
> 2. vi /etc/lcovrc
>     Change line: lcov_gcov_dir = /proc/gcov to lcov_gcov_dir = /proc/xen/gcov
> 3. # cd  /tmp; lcov -c -o kernel.info
> 4. # genhtml kernel.info
> 5, # firefox index.html
> 
> lcov README and screenshot is attached.

22% coverege, eh? Is that just by booting the Dom0 kernel?

> 
> HTH
> 
> Note:
> For any other detail required please CC me to parkash.tej@gmail.com

> diff -r 86d6c6417cf9 drivers/xen/Kconfig
> --- a/drivers/xen/Kconfig	Thu Feb 04 13:08:27 2010 +0000
> +++ b/drivers/xen/Kconfig	Sun Feb 07 00:13:40 2010 +0530
> @@ -311,6 +311,13 @@
>  	help
>  	  Xen hypervisor attributes will show up under /sys/hypervisor/.
>  
> +config XEN_GCOV_PROC
> +       tristate "Code covarage for hypervisor"
                          ^^^^^ - coverage