Messages in this thread | | | Date | Tue, 24 May 2011 17:40:20 +0200 | From | Ingo Molnar <> | Subject | Re: perf: regression with PERF_EVENT_IOC_REFRESH |
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* Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:
> On Tue, 2011-05-24 at 11:04 -0400, Vince Weaver wrote: > > > 2.6.37, 2.6.38, or 2.6.39 then it would be silly to do it just for > > 2.6.40.
No, this commit was added in v2.6.38 so v2.6.37 should be fine.
> Oh, I assumed it was recent and .39/.40 would suffice.
Btw., how did it happen that the PAPI tests did not get run against upstream over the course of about half a year, two full stable kernels released:
Date: Mon Mar 14 18:20:32 2011 -0700 Linux 2.6.38 Date: Wed May 18 21:06:34 2011 -0700 Linux 2.6.39
?
I'd suggest periodically running the PAPI tests on the perf development tree:
http://people.redhat.com/mingo/tip.git/README
doing that would have caught this problem 6 months ago.
The upstream policy is that regressions are generally recognized before the next kernel gets released: i.e. in the stabilization period after -rc1, the roughly two months until the final kernel gets released. That is the window when we can still fix regressions relatively cheaply.
Yes, there are exceptions, but if a piece of user-space code did not get tested with upstream over months and months then that moves into the 'fix it if we can' category - not a regression per se.
So the upstream message is: we can only care about you if you care testing upstream.
So if it's easy to fix we can certainly fix this bug and mark it for a -stable backport, but this is not a regression that got reported to us in any timely manner.
Btw., to get such assumptions tested more frequently than twice a year i'd suggest moving these usecases into 'perf test' or so - that it gets run every day:
$ perf test 1: vmlinux symtab matches kallsyms: FAILED!
2: detect open syscall event: Ok 3: detect open syscall event on all cpus: Ok 4: read samples using the mmap interface: Ok
Thanks,
Ingo
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