Re: Test 3 (Was: Lock elision test results)

[Dominik Vogt <vogt at linux dot vnet dot ibm dot com>]

On Tue, Jul 02, 2013 at 02:18:04PM +0200, Torvald Riegel wrote:
> On Fri, 2013-06-14 at 12:26 +0200, Dominik Vogt wrote:
> > Test 3 (cacheline pingpong)
> > ======

> > Test execution
> > --------------
> > 
> > Identical to test 1.
> > 
> > Result
> > ------
> > 
> > (1) unpatched  : 100.00%
> > (2) old glibc  : 103.94%
> > (3) elision off:  76.25%
> > (4) elision on : 373.38%
> 
> So in this case we scale almost linearly, nice.  Do you know why it is
> different in test 1?  Just the abort ratio as cause of this would be
> kind of surprising, given that abort rates differ not that much

> (or aborts would have to be really costly).

Aborts _are_ expensive.

> > The abort ratio in (4) in all threads is < 0.01%.
> 
> In general, I think it would be good if you could port these tests to
> the performance benchmark framework that Siddhesh has been working on,
> and contribute them to glibc.  This way, we can also work on avoiding
> performance regressions as the one you reported for the 2.15 vs. current
> case without the elision patches.

I can look into this when I have the clearancy to post source
code.

Ciao

Dominik ^_^  ^_^

-- 

Dominik Vogt
IBM Germany