[PATCH 1/2] perf: add container identifier entry in perf sample data

[Hari Bathini]

Currently, there is no mechanism to filter events based on containers.
perf -g can be used, but it will not filter events for the containers
created after perf is invoked, making it difficult to assess/analyze
performance issues of multiple containers at once. This limitation can
be overcome, if there is a standard kernel identifier for containers.

This patch introduces a container identifier entry field in perf sample
data to identify or distinguish sample data of different containers. It
uses the cgroup namespace inode number of a given task as it's container
identifier (cid). Alternatively, inode number of pid namespace can also
be used as cid. This patch assumes each container is created with it's
own cgroup namespace.

Suggested-by: Ananth N Mavinakayanahalli <ana...@linux.vnet.ibm.com>
Signed-off-by: Hari Bathini <hbath...@linux.vnet.ibm.com>
---
 include/linux/perf_event.h      |    4 ++++
 include/uapi/linux/perf_event.h |    3 ++-
 kernel/events/core.c            |   15 +++++++++++++++
 3 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 8ed43261..d43bbf2 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -904,6 +904,10 @@ struct perf_sample_data {
 
        struct perf_regs                regs_intr;
        u64                             stack_user_size;
+       struct {
+               u32     cid;
+               u32     reserved;
+       }                               cid_entry;
 } ____cacheline_aligned;
 
 /* default value for data source */
diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index c66a485..fb4f902 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -139,8 +139,9 @@ enum perf_event_sample_format {
        PERF_SAMPLE_IDENTIFIER                  = 1U << 16,
        PERF_SAMPLE_TRANSACTION                 = 1U << 17,
        PERF_SAMPLE_REGS_INTR                   = 1U << 18,
+       PERF_SAMPLE_CID                         = 1U << 19,
 
-       PERF_SAMPLE_MAX = 1U << 19,             /* non-ABI */
+       PERF_SAMPLE_MAX = 1U << 20,             /* non-ABI */
 };
 
 /*
diff --git a/kernel/events/core.c b/kernel/events/core.c
index a19550d..b5d774c 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -5716,6 +5716,9 @@ void perf_output_sample(struct perf_output_handle *handle,
                }
        }
 
+       if (sample_type & PERF_SAMPLE_CID)
+               perf_output_put(handle, data->cid_entry);
+
        if (!event->attr.watermark) {
                int wakeup_events = event->attr.wakeup_events;
 
@@ -5849,6 +5852,18 @@ void perf_prepare_sample(struct perf_event_header 
*header,
 
                header->size += size;
        }
+
+       if (sample_type & PERF_SAMPLE_CID) {
+               int size = sizeof(u64);
+
+               /*
+                * Container identifier for a given task.
+                * Using cgroup namespace inode number for this.
+                */
+               data->cid_entry.cid = current->nsproxy->cgroup_ns->ns.inum;
+               data->cid_entry.reserved = 0;
+               header->size += size;
+       }
 }
 
 static void __always_inline