[PATCH v3] powerpc: strstr optimization

[Tulio Magno Quites Machado Filho]

"Carlos O'Donell" <carlos@redhat.com> writes:

> On 07/16/2015 03:55 PM, Ondřej Bílka wrote:
>> Sorry Carlos, your trust is misplaced. This patch wasn't reviewed at
>> all. I did that as test how much we could test IBM to verify patches. 

No.  That isn't true.
I reviewed this patch myself.  All the 4 versions.
So did Steven.

>> I pointed out that it could have possibly quadratic behaviour which
>> still does. So please don't accept unreviewed patches next time.

Yes, this patch does have a quadratic worst case as does quicksort.
But for both algorithms, they're clearly an improvement over what was
available before them.
Is this algorithm perfect?  No.  I don't believe such a thing exist.  I
believe in iterative improvements.

> They showed cases for which the code does go faster and objectively
> so using the microbenchmark, and that's a win for now. Please continue 
> to work with IBM to remove the quadratic worst case.

That's our intention.
An improvement to this implementation is already in our backlog (i.e. we
haven't started yet) and I'd be glad if someone is interested to help us with
this.

> Tulio, You will need to work out why you have quadratic worst case.
> It's certainly something we try to avoid. Did you make a particular
> decision not to avoid it?

IMHO, the overall improvement brought by this patch is more important than
the worst case scenario Ondřej is showing.
Which doesn't mean we're neglecting the quadratic worst case.

-- 
Tulio Magno