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RE: [Xen-devel] [PATCH] IRQ Cleanup: rename nr_ioapic_registers to nr_ioapic_entries

> From: Keir Fraser [mailto:keir.xen@xxxxxxxxx]
> Sent: Monday, September 26, 2011 10:27 AM
> To: Konrad Rzeszutek Wilk; Andrew Cooper
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxx; Jan Beulich
> Subject: Re: [Xen-devel] [PATCH] IRQ Cleanup: rename nr_ioapic_registers to 
> nr_ioapic_entries
> On 26/09/2011 08:45, "Konrad Rzeszutek Wilk" <konrad.wilk@xxxxxxxxxx> wrote:
> >> I guess it depends on whether you consider that we should stay in line
> >> with Linux or not.  While the code did start in Linux, it has diverged
> >
> > Stay. Intel does a lot of work of "lift from Linux" and drop in Xen
> > code. There is similarity.
> You might also say it gives a false sense of similarity. Andrew's now having
> to go fix the per-cpu vector stuff for example. It got dropped in; it was
> complex and opaque; it doesn't really work properly yet. I'd prefer the
> people doing the porting to have to think about each line a bit more.

You also don't want the people doing the porting thinking about each
line so hard that they decide to rewrite all of them to meet their
own personal preference.  Remember that the number of people familiar
with "code X" on Linux probably outnumbers the number of people
familiar with code X on Xen by a factor of 10-100.  The point of
stealing the Linux code to begin with is to leverage developer
knowledge and (historical) maintenance knowledge.

A suggested compromise:  Any divergence of this sort from Linux should
be explicitly noted in a comment, e.g. "Linux calls this foo, but Xen
calls it bar, though they otherwise should function very similarly".


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