This whole debate saddens me

Posted Dec 4, 2014 14:08 UTC (Thu) by dan_a (guest, #5325)
In reply to: This whole debate saddens me by mjg59
Parent article: The "Devuan" Debian fork

But then wouldn't Red Hat start doing all of that - because they will want to solve the regression?

This whole debate saddens me

Posted Dec 4, 2014 20:07 UTC (Thu) by mjg59 (subscriber, #23239) [Link] (2 responses)

My experience at Red Hat was that performance issues were generally diagnosed by looking at perf traces and making targeted attempts at fixing the issue rather than just bisecting - the parts of the kernel that tend to cause this issues are frequently rewritten between RHEL releases, so bisecting often just gives you "We changed this algorithm to this other algorithm", and you still need to figure out why it's pathological with the new implementation because just reverting that isn't an option.

This whole debate saddens me

Posted Dec 4, 2014 20:44 UTC (Thu) by viro (subscriber, #7872) [Link] (1 responses)

Do we, by any chance, have magical private perf patches that allow to obtain information about an apparent race leading to data corruption sometime reproducible by given test in xfstests, and whom should I ask for it? Just going by the last time I had to go into "bisect all the way to 3.0" mode...

</sarcasm> There's a whole lot of stuff other than performance regressions, as you damn well know. For those, yes, you want perf traces first and foremost (and even then you really might want to see where the hell has regression first happened - sometimes it helps in figuring out what's wrong with the current algorithm). And we do upstream work as well, as you also know - after all, crap happening in mainline eventually will end up as crap happening in the next RHEL branch. <sarcasm>

This whole debate saddens me

Posted Dec 4, 2014 21:02 UTC (Thu) by mjg59 (subscriber, #23239) [Link]

Undeniably. But they're still not cases where customers are going to try to swap out individual components themselves - the risk is customers being unhappy because it takes Red Hat longer to diagnose an issue, not customers being unhappy that they can't run hybrid RHEL systems.