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perf report: Sort child tasks by tid

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Commit 91e467bc56 ("perf machine: Use hashtable for machine
threads") made the iteration of thread tids unordered. The perf report
--tasks output now shows child threads in an order determined by the
hashing. For example, in this snippet tid 3 appears after tid 256 even
though they have the same ppid 2:

```
$ perf report --tasks
%      pid      tid     ppid  comm
         0        0       -1 |swapper
         2        2        0 | kthreadd
       256      256        2 |  kworker/12:1H-k
    693761   693761        2 |  kworker/10:1-mm
   1301762  1301762        2 |  kworker/1:1-mm_
   1302530  1302530        2 |  kworker/u32:0-k
         3        3        2 |  rcu_gp
...
```

The output is easier to read if threads appear numerically
increasing. To allow for this, read all threads into a list then sort
with a comparator that orders by the child task's of the first common
parent. The list creation and deletion are created as utilities on
machine.  The indentation is possible by counting the number of
parents a child has.

With this change the output for the same data file is now like:
```
$ perf report --tasks
%      pid      tid     ppid  comm
         0        0       -1 |swapper
         1        1        0 | systemd
       823      823        1 |  systemd-journal
       853      853        1 |  systemd-udevd
      3230     3230        1 |  systemd-timesyn
      3236     3236        1 |  auditd
      3239     3239     3236 |   audisp-syslog
      3321     3321        1 |  accounts-daemon
...
```

Signed-off-by: Ian Rogers <irogers@google.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Yang Jihong <yangjihong1@huawei.com>
Cc: Oliver Upton <oliver.upton@linux.dev>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20240301053646.1449657-2-irogers@google.com
This commit is contained in:
Ian Rogers
2024-02-29 21:36:39 -08:00
committed by Namhyung Kim
parent 498d348637
commit 2f1e20feb9
3 changed files with 172 additions and 93 deletions
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10
tools/perf/util/machine.h
View File

@@ -280,6 +280,16 @@ int machines__for_each_thread(struct machines *machines,
int (*fn)(struct thread *thread, void *p),
void *priv);
struct thread_list {
struct list_head list;
struct thread *thread;
};
/* Make a list of struct thread_list based on threads in the machine. */
int machine__thread_list(struct machine *machine, struct list_head *list);
/* Free up the nodes within the thread_list list. */
void thread_list__delete(struct list_head *list);
pid_t machine__get_current_tid(struct machine *machine, int cpu);
int machine__set_current_tid(struct machine *machine, int cpu, pid_t pid,
pid_t tid);