Re: [Xen-devel] Question about xentrace to trace s_time_t type of data

[Meng Xu <xumengpanda@xxxxxxxxx>]

Hi Konrad,

2014-08-25 12:39 GMT-04:00 Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>:

. snip..
> > > Thank you very much for your time!
> >
> > I have to be honest I hadn't actually dug in what was underneath
> > the macro. Just been using the macro and it had worked for me.
> >
> >
> âThank you for your time, anyway! :-)
>
> I think the issue is when I tried to trace a type of data larger than
> 32bits, such as the type s_time_t, the trace_var() result becomes
> uninterpretable. Maybe I should never simply pass a type of data larger
> than 32bit to trace macro, but I don't know (and I hope to know) why. :-(

Oh, probably because of not packing. I would split all your
data types to be within a 32-bit unsigned int member. You can use
bit shiffting to pack data.

I presume the macros "fix" this for me as they will warn me when I try
to use an 64-bit value and I've had always to play the << game to "fit"
an 64-bit value in (by using two 32-bit arguments).

âI see. ÂI did use the bit shifting to pack a 64bit data to two 32bit unsigned int in my previous rt scheduler patch.Â

Thank you very much for confirming the workable approach! :-Pâ

Best,

âMengâ

--

-----------
Meng Xu
PhD Student in Computer and Information Science
University of Pennsylvania

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