Messages in this thread | | | Subject | Re: [PATCH v4 1/3] perf: add PERF_RECORD_NAMESPACES to include namespaces related info | From | Hari Bathini <> | Date | Wed, 21 Dec 2016 18:39:01 +0530 |
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Hi Peter,
On Saturday 17 December 2016 01:35 AM, Peter Zijlstra wrote: > On Fri, Dec 16, 2016 at 11:51:20PM +0530, Hari Bathini wrote: >> Hi Peter, >> >> >> On Friday 16 December 2016 01:27 PM, Peter Zijlstra wrote: >>> On Fri, Dec 16, 2016 at 11:57:47AM +0530, Hari Bathini wrote: >>>> On Friday 16 December 2016 12:16 AM, Peter Zijlstra wrote: >>>>> On Fri, Dec 16, 2016 at 12:07:06AM +0530, Hari Bathini wrote: >>>>>> +struct perf_ns_link_info { >>>>>> + __u64 dev; >>>>>> + __u64 ino; >>>>>> +}; >>>>>> + >>>>>> +enum { >>>>>> + NET_NS_INDEX = 0, >>>>>> + UTS_NS_INDEX = 1, >>>>>> + IPC_NS_INDEX = 2, >>>>>> + PID_NS_INDEX = 3, >>>>>> + USER_NS_INDEX = 4, >>>>>> + MNT_NS_INDEX = 5, >>>>>> + CGROUP_NS_INDEX = 6, >>>>>> + >>>>>> + NAMESPACES_MAX, /* maximum available namespaces */ >>>>>> +}; >>>>>> + >>>>>> enum perf_event_type { >>>>>> /* >>>>>> @@ -862,6 +880,17 @@ enum perf_event_type { >>>>>> */ >>>>>> PERF_RECORD_SWITCH_CPU_WIDE = 15, >>>>>> + /* >>>>>> + * struct { >>>>>> + * struct perf_event_header header; >>>>>> + * u32 pid; >>>>>> + * u32 tid; >>>>>> + * struct namespace_link_info link_info[NAMESPACES_MAX]; >>>>>> + * struct sample_id sample_id; >>>>>> + * }; >>>>>> + */ >>>>>> + PERF_RECORD_NAMESPACES = 16, >>>>>> + >>>>>> PERF_RECORD_MAX, /* non-ABI */ >>>>>> }; >>>>> What happens if a future kernel adds another namespace? >>>>> >>>> No impact unless NAMESPACES_MAX in include/uapi/linux/perf_event.h is >>>> updated to accommodate that.. >>>> And if it is updated, the corresponding change is expected in perf-tool as >>>> well.. >>> And what happens if you try and process old data files with the new >>> tools or the other way around? >> It works fine either way. I tested that.. > I don't see how the tool can parse old records (with NAMESPACES_MAX == > 7) if you set its NAMESPACES_MAX to say 10. > > Then it will expect the link_info array to be 10 entries and either read > past the end of the record (if !sample_all) or try and interpret > sample_id as link_info records. >
Right. There will be inconsistency with data the perf tool tries to read beyond what the kernel supports. IIUC, you mean, include nr_namespaces field in the record and warn the user if it doesn't match with the one perf-tool supports before proceeding..?
Thanks Hari
PS: I am on vacation. Will post next version early January.
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