Messages in this thread | | | Date | Wed, 27 Nov 2013 12:52:47 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH] perf tools: Fix not finding kcore in buildid cache |
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* Adrian Hunter <adrian.hunter@intel.com> wrote:
> On 27/11/13 13:32, Ingo Molnar wrote: > > > > * Adrian Hunter <adrian.hunter@intel.com> wrote: > > > >> On 26/11/13 18:15, Ingo Molnar wrote: > >>> > >>> * Adrian Hunter <adrian.hunter@intel.com> wrote: > >>> > >>>> The logic was not looking in the buildid cache for kcore > >>>> if the host kernel buildid did not match the recorded > >>>> kernel buildid. > >>> > >>> It would be nice to also include the specific failure mode in the > >>> changelog: exactly how can users run into this. That will be more > >>> useful to most people reading these changelogs than a more abstract > >>> bug description. > >> > >> The preconditions for the problem are that kcore is in the buildid > >> cache and that the running kernel has a different buildid e.g. > >> > >> $ perf buildid-list | grep kernel.kallsyms > >> b18fbe769dea12513028a4287dae02efc1582c29 [kernel.kallsyms] > >> > >> $ perf record -o /tmp/junk true >/dev/null 2>&1 ; perf buildid-list -i /tmp/junk | grep kernel.kallsyms > >> 504f9fd9328c40714995ce76fe1354c6e90136ce [kernel.kallsyms] > >> > >> > >> > >> Before the patch: > >> > >> > >> $ perf script -v >out.txt > >> build id event received for [kernel.kallsyms]: b18fbe769dea12513028a4287dae02efc1582c29 > >> <SNIP> > >> Using /home/ahunter/.debug/[kernel.kallsyms]/b18fbe769dea12513028a4287dae02efc1582c29 for symbols > >> > >> perf script stopped > >> > >> > >> After the patch: > >> > >> > >> $ perf script -v >out.txt > >> build id event received for [kernel.kallsyms]: b18fbe769dea12513028a4287dae02efc1582c29 > >> <SNIP> > >> Using /home/ahunter/.debug/[kernel.kcore]/b18fbe769dea12513028a4287dae02efc1582c29/2013112617084061/kcore for kernel object code > >> Using /home/ahunter/.debug/[kernel.kcore]/b18fbe769dea12513028a4287dae02efc1582c29/2013112617084061/kallsyms for symbols > >> > >> perf script stopped > > > > So the result of the patch is that kernel symbols get > > resolved/annotated correctly, as expected from the live kcore feature, > > right? > > Yes but this is the non-live case i.e. the kernel has changed and we are > looking at a special copy of kcore that we placed in the buildid cache > (using "perf buildid-cache -v -k /proc/kcore") when the data was recorded.
Okay.
Thanks,
Ingo
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