Re: [ltt-dev] [PATCH] Fix dirty page accounting in redirty_page_for_writepage()

Mathieu Desnoyers
2009-04-30T16:03:34Z

* Ingo Molnar (mingo@elte.hu) wrote:
>
> * Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> wrote:
>
> > * Ingo Molnar (mingo@elte.hu) wrote:
> > >
> > > * Christoph Lameter <cl@linux.com> wrote:
> > >
> > > > On Wed, 29 Apr 2009, Mathieu Desnoyers wrote:
> > > >
> > > > > to have a good look at the memory accounting code. We could
> > > > > probably benefit of Christoph Lameter's cpu ops (using segment
> > > > > registers to address per-cpu variables with atomic inc/dec) in
> > > > > there. Or at least removing interrupt disabling by using preempt
> > > > > disable and local_t variables for the per-cpu counters could
> > > > > bring some benefit.
> > > >
> > > > Guess we are ready for atomic per cpu ops now that the new per cpu
> > > > allocator is in? Segment register issues with the PDA are also
> > > > solved right?
> > >
> > > it's all done, implemented and upstream already. You are a bit late
> > > to the party ;-)
> > >
> > > Ingo
> >
> > Or way too early, depending on the point of view. :-)
> >
> > e.g.
> > http://lkml.org/lkml/2008/5/30/3
> >
> > I think Christoph deserves credits for pioneering this area with fresh
> > ideas.
>
> Ok, i didnt want to go there - but let me correct this version of
> history.
>
> Christoph's zero-based x86 percpu patches were incomplete and never
> worked reliably - Christoph unfortunately never addressed the
> bugs/crashes i reported. (and Mike Travis and me injected quite a
> bit of testing into it) There were two failed attempts to productize
> them and the patches just bitrotted for more than a year.
>
> Tejun on the other hand fixed those problems (four of Christoph's
> patches survived more or less and were credited to Christoph) and
> did more than 50 highly delicate patches of far larger complexity to
> solve the _whole_ problem range - within a two months timeframe.
>
> Ideas and half-done patches covering <10% of the work needed are not
> enough. Being able to implement it and productize it is the real
> deal, in my book.
>
> Thanks goes to Christoph (and Rusty) for coming up with the idea,
> but it would be manifestly unfair to not send 90% of the kudos to
> Tejun for turning it all into reality and fixing all the other
> problems and redesigning almost all the x86 percpu code in the
> process! ;-)
>

Then thanks to Christoph, Rusty and to Tejun for the respective effort
they did. My goal is surely only to recognise their respective credit.

Mathieu

> Ingo
>
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Mathieu Desnoyers
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