Messages in this thread | | | From | Linus Torvalds <> | Date | Sun, 8 Dec 2019 10:04:51 -0800 | Subject | Re: [PATCH 0/2] pipe: Fixes [ver #2] |
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On Sun, Dec 8, 2019 at 8:46 AM Akemi Yagi <toracat@elrepo.org> wrote: > > I forgot to mention that the aforementioned bug in make was originally > reported for Fedora. They now have a patched version of make > (make-4.2.1-15.fc32) in Rawhide.
Yes, as mentioned I do expect it's some jobserver interaction - I've seen bad jobserver behavior before. But my 'make' hasn't been upgraded since May, as far as I can tell from my logs, so the huge performance regression was new.
So the huge slowdown is real, and was triggered by the kernel changes. But yes, it's entirely possible - even likely - that it's due to a jobserver bug that ends up being sensitive to scheduling.
We do treat even "user space is buggy and shouldn't have done that" as a regression.
It's annoying. Timing-related issues are some of the worst to debug. Particularly when (at least I) primarily debug by looking at the code and trying to see what's wrong that way.
Linus
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