clang's build performance

["René J.V. Bertin"]

On Jul 07, 2014, at 12:39, Ian Wadham wrote:

Now why did I misread and wonder why Apple would have a Real Men column on a site called Activity Monitor? :)))

> FWIW, and this is perhaps completely off-topic, I find that Clang performs

No, I think it's perfectly on topic.

> well enough almost all of the time.  However, sometimes it expands
> seemingly without limit, both in wall clock time and memory space (as
> reported by the Real Mem column of Apple's Activity Monitor).  This

I had this with clang-3.3 (less with 3.4) building 1 particular file of Calligra, which would take about an hour in which virtual memory peaked at nearly 20Gb (not it was probably much less than that when the process stalled). Very reproducible, but only on OS X 10.6 . Same, CPU usage was extremely low for such a hogging process, but that can simply be because swapping activity is not imputed to the process it's done for?

> Could episodes like this be affecting Clang performance measurements?

I think not, because as you say those kind of episodes have low CPU usage. So they'd also decrease the average/overall CPU usage reported after the build process completes, and that's not the case.

BTW, I couldn't get kdelibs4 to build with macports-clang-3.4 yesterday (when testing the patch I submitted later). It got stuck on a file called parser.cpp, but this time without eating all memory.

Cheers,
René