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Re: [Xen-devel] [PATCH-0/2] Hypervisor profiling using GCOV (64bit Hype

To: Gianluca Guida <Gianluca.Guida@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH-0/2] Hypervisor profiling using GCOV (64bit Hypervisor)
From: Tej <bewith.tej@xxxxxxxxx>
Date: Mon, 6 Apr 2009 20:34:18 +0530
Cc: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
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On Thu, Mar 26, 2009 at 4:27 PM, Gianluca Guida
<Gianluca.Guida@xxxxxxxxxxxxx> wrote:
> Hi,
> Sorry for the late reply.
> On Mar 26, 2009, at 7:59 AM, Tej wrote:
>> On Mon, Mar 2, 2009 at 9:36 PM, Tej <bewith.tej@xxxxxxxxx> wrote:
>>> On Sat, Feb 28, 2009 at 12:32 AM, Gianluca Guida
>>> <gianluca.guida@xxxxxxxxxxxxx> wrote:
>>>> While I still need to test the patch (building 3.3 right now) and to
>>>> understand gcov internals, I think that a few comments can be done,
>>>> mostly
>>>> aestethicals.
>>>> - xen coding style: Using four-spaces tabs is generally the tradition.
>>>> Also
>>>> I do prefer to have brackets that start code blocks on a new line
>>>> aligned to
>>>> the previous line, but that's not followed everywhere in the code.
>>>> - Makefiles: while the num=$*.c is still a mystery to me, my question
>>>> is: do
>>>> you really need to make links with different names to files compiled
>>>> multiple times? If so, it would be useful to remove them on 'make
>>>> clean'.
>>>> Also, it would be useful to make this feature enabled with a
>>>> compile-time
>>>> option.
>>> Attached patches address the four-spaces tabs and make clean issues.
>>> Hope the code is more clean and readable
>> Hi
>> Sorry for interrupting you guys from your busy schedule, as i just
>> want to know the current status for GCOV patches i submitted early
>> this month.
>> any feedback on "testing/coding/design/feature" will be appreciated.
> I've been testing it for a while, and it seems an useful and interesting
> feature.
> A few comments, though:
> - As I said, while the patch is minimal enough, the feature requires some
> intrusive changes in Xen, like changing the linker script (via the
> definition of CONSTRUCTORS) and in general it changes the compiler behavior,
> so I think it should be mandatory to make this feature explicitely enabled
> at compile time, e.g.  gcov=y.

patches attached added the compile time options gcov=y
a small readme is attached, which can be probably help in compiling
correctly at first time

gcov=n (default) disable every code part added by xen-gcov-core patch
(entry.S, core module, gcov constructor etc.)

Now in case, we have configured proc module (y || m) but did not use
gcov=y  option during compilation then proc module refuses to insert
as there is no hypercall added for gcov and we return -ENOENT (insmod
error type). Better suggestion are more than welcome

(i really don't know if we can make Kernel configuration and xen
configuration in sync e.g gcov=y depends on Kconfig "xen-gcov-proc" or
vice versa)

> - I am talking about Xen code only, but I think a few part of the codes
> should be more clear. I find very confusing the difference between
> xen_gcov_info and gcov_info, and all the instructions that uses them. A
> better naming scheme for the variables and more comments would be
> appreciated.

this issue still we are working on it. But if we keep two structure as
it is then we will have less complex core and proc implementation.


Sorry for some delay.

> Thanks!
> Gianluca

Attachment: linux-2.6.18-gcov-v4.patch
Description: Binary data

Attachment: xen-3.3-gcov-v4.patch
Description: Binary data

Attachment: gcov-readme
Description: Binary data

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