Messages in this thread | | | From | Linus Torvalds <> | Date | Thu, 13 Dec 2012 08:03:58 -0800 | Subject | Re: [GIT PULL] perf changes for v3.8 |
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On Thu, Dec 13, 2012 at 6:30 AM, David Ahern <dsahern@gmail.com> wrote: > > One of the problems is that existing binaries set the exclude_guest flag > (https://lkml.org/lkml/2012/7/9/292).
[ to zero ]
Yeah. And it apparently *never* worked. So it's not a regression.
> So, requesting users to update their binaries if they want to use precise > sampling is not acceptable. A 100% catastrophic failure of all running VMs > is acceptable? All VMs will crash and there is no direct causal > relationship.
So instead, you expect everybody else - for whom things *used* to work - to upgrade their binary, or their scripts, or just start using an insane command line flag that makes no sense for them? Forcing non-virtualization users to use a "only trace the host" flag is crazy.
Either way, somebody will be unhappy. No question about that. But our rule in the kernel is "no regressions".
Now, I do agree that for "perf", it's fairly easy to say "just recompile". I can do it in seconds, and it would presumably solve my problem by just making the "host only" case the default, and I don't need the "H" any more.
But that whole "no regressions" really is important. I can work around things very easily, but the "no regressions" rule really means that I should never *need* to work around things.
So when I see a regression, I consider it a major bug, even if the workaround is trivial.
Linus
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