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Date: Mon, 14 Nov 2016 16:02:30 +0530
From: Hari Bathini <hbathini@...ux.vnet.ibm.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: ast@...com, lkml <linux-kernel@...r.kernel.org>, acme@...nel.org,
alexander.shishkin@...ux.intel.com, mingo@...hat.com,
daniel@...earbox.net, rostedt@...dmis.org,
Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>,
ebiederm@...ssion.com, sargun@...gun.me,
Aravinda Prasad <aravinda@...ux.vnet.ibm.com>,
brendan.d.gregg@...il.com
Subject: Re: [PATCH 1/3] perf: add PERF_RECORD_NAMESPACES to include
namespaces related info
On Thursday 10 November 2016 06:49 PM, Peter Zijlstra wrote:
> On Thu, Nov 10, 2016 at 05:08:06PM +0530, Hari Bathini wrote:
>
>> diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
>> index c66a485..575aed6 100644
>> --- a/include/uapi/linux/perf_event.h
>> +++ b/include/uapi/linux/perf_event.h
>> @@ -344,7 +344,8 @@ struct perf_event_attr {
>> use_clockid : 1, /* use @clockid for time fields */
>> context_switch : 1, /* context switch data */
>> write_backward : 1, /* Write ring buffer from end to beginning */
>> - __reserved_1 : 36;
>> + namespaces : 1, /* include namespaces data */
>> + __reserved_1 : 35;
>>
>> union {
>> __u32 wakeup_events; /* wakeup every n events */
>> @@ -862,6 +863,24 @@ enum perf_event_type {
>> */
>> PERF_RECORD_SWITCH_CPU_WIDE = 15,
>>
>> + /*
>> + * struct {
>> + * struct perf_event_header header;
>> + *
>> + * u32 pid, tid;
>> + * u64 time;
>> + * u32 uts_ns_inum;
>> + * u32 ipc_ns_inum;
>> + * u32 mnt_ns_inum;
>> + * u32 pid_ns_inum;
>> + * u32 net_ns_inum;
>> + * u32 cgroup_ns_inum;
>> + * u32 user_ns_inum;
>> + * struct sample_id sample_id;
>> + * };
>> + */
>> + PERF_RECORD_NAMESPACES = 16,
> So this format is not extensible, that is, if someone adds yet another
> namespace, we'll need to introduce PERF_RECORD_NAMESPACES2.
>
> Is there a 'natural' and exposed namespace index that we can use to
> change it like:
>
> u32 nr_nss;
> u32 namespace[nr_nss];
>
> ?
Hi Peter,
Nothing of that sort exists, currently.
Maybe, time to introduce with this patch-set..?
>> +static void perf_event_namespaces_output(struct perf_event *event,
>> + void *data)
>> +{
>> + struct perf_namespaces_event *namespaces_event = data;
>> + struct perf_output_handle handle;
>> + struct perf_sample_data sample;
>> + int size = namespaces_event->event_id.header.size;
>> + struct nsproxy *nsproxy;
>> + int ret;
>> +
>> + if (!perf_event_namespaces_match(event))
>> + return;
>> +
>> + perf_event_header__init_id(&namespaces_event->event_id.header,
>> + &sample, event);
>> + ret = perf_output_begin(&handle, event,
>> + namespaces_event->event_id.header.size);
>> +
>> + if (ret)
>> + goto out;
> If you were to introduce:
>
> struct ns_event_id *ei = &namespace_event->event_id;
>
>> +
>> + namespaces_event->event_id.pid = perf_event_pid(event,
>> + namespaces_event->task);
>> + namespaces_event->event_id.tid = perf_event_tid(event,
>> + namespaces_event->task);
>> +
>> + if (namespaces_event->task != current)
>> + task_lock(namespaces_event->task);
>> +
>> + nsproxy = namespaces_event->task->nsproxy;
>> + if (nsproxy != NULL) {
>> + namespaces_event->event_id.uts_ns_inum =
>> + nsproxy->uts_ns->ns.inum;
>> +#ifdef CONFIG_IPC_NS
>> + namespaces_event->event_id.ipc_ns_inum =
>> + nsproxy->ipc_ns->ns.inum;
>> +#endif
>> + namespaces_event->event_id.mnt_ns_inum =
>> + nsproxy->mnt_ns->ns.inum;
>> + namespaces_event->event_id.pid_ns_inum =
>> + nsproxy->pid_ns_for_children->ns.inum;
>> +#ifdef CONFIG_NET
>> + namespaces_event->event_id.net_ns_inum =
>> + nsproxy->net_ns->ns.inum;
>> +#endif
>> +#ifdef CONFIG_CGROUPS
>> + namespaces_event->event_id.cgroup_ns_inum =
>> + nsproxy->cgroup_ns->ns.inum;
>> +#endif
>> + }
>> +
>> + namespaces_event->event_id.user_ns_inum =
>> + __task_cred(namespaces_event->task)->user_ns->ns.inum;
> You can do s/namespace_event->event_id./ei->/ which is tons shorter and
> would result in less wrapping of lines and generally improve
> readability.
True.
>> +
>> + if (namespaces_event->task != current)
>> + task_unlock(namespaces_event->task);
>> +
>> + namespaces_event->event_id.time = perf_event_clock(event);
>> +
>> + perf_output_put(&handle, namespaces_event->event_id);
>> +
>> + perf_event__output_id_sample(event, &handle, &sample);
>> +
>> + perf_output_end(&handle);
>> +out:
>> + namespaces_event->event_id.header.size = size;
>> +}
>> +
>> +void perf_event_namespaces(struct task_struct *task)
>> +{
>> + struct perf_namespaces_event namespaces_event;
>> +
>> + if (!atomic_read(&nr_namespaces_events))
>> + return;
>> +
>> + namespaces_event = (struct perf_namespaces_event){
>> + .task = task,
>> + .event_id = {
>> + .header = {
>> + .type = PERF_RECORD_NAMESPACES,
>> + .misc = 0,
>> + .size = sizeof(namespaces_event.event_id),
>> + },
>> + /* .pid */
>> + /* .tid */
>> + /* .time */
>> + /* .uts_ns_inum */
>> + /* .ipc_ns_inum */
>> + /* .mnt_ns_inum */
>> + /* .pid_ns_inum */
>> + /* .net_ns_inum */
>> + /* .cgroup_ns_inum */
>> + /* .user_ns_inum */
>> + },
>> + };
>> +
>> + perf_iterate_sb(perf_event_namespaces_output,
>> + &namespaces_event,
>> + NULL);
>> +}
>> diff --git a/kernel/fork.c b/kernel/fork.c
>> index 997ac1d..3faca3d 100644
>> --- a/kernel/fork.c
>> +++ b/kernel/fork.c
>> @@ -1818,6 +1818,7 @@ static __latent_entropy struct task_struct *copy_process(
>> cgroup_post_fork(p);
>> threadgroup_change_end(current);
>> perf_event_fork(p);
>> + perf_event_namespaces(p);
> I would much prefer calling perf_event_namespace() from
> perf_event_fork() and reduce the external interface.
>
OK. Will update..
Thanks
Hari
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