On Mon, Nov 19, 2012 at 11:36:04PM +0100, Ingo Molnar wrote:

* Mel Gorman [off-list ref] wrote:

quoted

Ok.

In response to one of your later questions, I found that I had 
in fact disabled THP without properly reporting it. [...]

Hugepages is a must for most forms of NUMA/HPC.

Requiring huge pages to avoid a regression is a mistake.

This alone 
questions the relevance of most of your prior numa/core testing 
results. I now have to strongly dispute your other conclusions 
as well.

I'll freely admit that disabling THP for specjbb was a mistake and I should
have caught why at the start. However, the autonumabench figures reported for
the last release had THP enabled as had the kernel build benchmark figures.

Just a look at 'perf top' output should have told you the story.

I knew THP were not in use and said so in earlier reports. Take this for
example -- https://lkml.org/lkml/2012/11/16/207 . For specjbb, note that
the THP fault alloc figures are close to 0 and due to that I said "THP is
not really a factor for this workload". What I failed to do was identify
why THP was not in use.

Yet time and time again you readily reported bad 'schednuma' 
results for a slow 4K memory model that neither we nor other 
NUMA testers I talked to actually used, without stopping to look 
why that was so...

Again, I apologise for the THP mistake. The fact remains that the other
implementations did not suffer a performance slowdown due to the same
mistake.

[ I suspect that if such terabytes-of-data workloads are forced 
  through such a slow 4K pages model then there's a bug or 
  mis-tuning in our code that explains the level of additional 
  slowdown you saw - we'll fix that.

  But you should know that behavior under the slow 4K model 
  tells very little about the true scheduling and placement 
  quality of the patches... ]

Please report proper THP-enabled numbers before continuing.

Will do. Are THP-disabled benchmark results to be ignored?

-- 
Mel Gorman
SUSE Labs

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