Em Thu, Aug 08, 2019 at 09:48:23AM +0300, Adrian Hunter escreveu: > Threads synthesized from /proc have comms with a start time of zero, and > not marked as "exec". Currently, there can be 2 such comms. The first is > created by processing a synthesized fork event and is set to the parent's > comm string, and the second by processing a synthesized comm event set to > the thread's current comm string. > > In the absence of an "exec" comm, thread__exec_comm() picks the last > (oldest) comm, which, in the case above, is the parent's comm string. For a > main thread, that is very probably wrong. Use the second-to-last in that > case.
Thanks, applied. - Arnaldo > This affects only db-export because it is the only user of > thread__exec_comm(). > > Example: > > $ sudo perf record -a -o pt-a-sleep-1 -e intel_pt//u -- sleep 1 > $ sudo chown ahunter pt-a-sleep-1 > > Before: > > $ perf script -i pt-a-sleep-1 --itrace=bep -s > tools/perf/scripts/python/export-to-sqlite.py pt-a-sleep-1.db branches calls > $ sqlite3 -header -column pt-a-sleep-1.db 'select * from comm_threads_view' > comm_id command thread_id pid tid > ---------- ---------- ---------- ---------- ---------- > 1 swapper 1 0 0 > 2 rcu_sched 2 10 10 > 3 kthreadd 3 78 78 > 5 sudo 4 15180 15180 > 5 sudo 5 15180 15182 > 7 kworker/4: 6 10335 10335 > 8 kthreadd 7 55 55 > 10 systemd 8 865 865 > 10 systemd 9 865 875 > 13 perf 10 15181 15181 > 15 sleep 10 15181 15181 > 16 kworker/3: 11 14179 14179 > 17 kthreadd 12 29376 29376 > 19 systemd 13 746 746 > 21 systemd 14 401 401 > 23 systemd 15 879 879 > 23 systemd 16 879 945 > 25 kthreadd 17 556 556 > 27 kworker/u1 18 14136 14136 > 28 kworker/u1 19 15021 15021 > 29 kthreadd 20 509 509 > 31 systemd 21 836 836 > 31 systemd 22 836 967 > 33 systemd 23 1148 1148 > 33 systemd 24 1148 1163 > 35 kworker/2: 25 17988 17988 > 36 kworker/0: 26 13478 13478 > > After: > > $ perf script -i pt-a-sleep-1 --itrace=bep -s > tools/perf/scripts/python/export-to-sqlite.py pt-a-sleep-1b.db branches calls > $ sqlite3 -header -column pt-a-sleep-1b.db 'select * from comm_threads_view' > comm_id command thread_id pid tid > ---------- ---------- ---------- ---------- ---------- > 1 swapper 1 0 0 > 2 rcu_sched 2 10 10 > 3 kswapd0 3 78 78 > 4 perf 4 15180 15180 > 4 perf 5 15180 15182 > 6 kworker/4: 6 10335 10335 > 7 kcompactd0 7 55 55 > 8 accounts-d 8 865 865 > 8 accounts-d 9 865 875 > 10 perf 10 15181 15181 > 12 sleep 10 15181 15181 > 13 kworker/3: 11 14179 14179 > 14 kworker/1: 12 29376 29376 > 15 haveged 13 746 746 > 16 systemd-jo 14 401 401 > 17 NetworkMan 15 879 879 > 17 NetworkMan 16 879 945 > 19 irq/131-iw 17 556 556 > 20 kworker/u1 18 14136 14136 > 21 kworker/u1 19 15021 15021 > 22 kworker/u1 20 509 509 > 23 thermald 21 836 836 > 23 thermald 22 836 967 > 25 unity-sett 23 1148 1148 > 25 unity-sett 24 1148 1163 > 27 kworker/2: 25 17988 17988 > 28 kworker/0: 26 13478 13478 > > Signed-off-by: Adrian Hunter <[email protected]> > Fixes: 65de51f93ebf ("perf tools: Identify which comms are from exec") > Cc: [email protected] > --- > tools/perf/util/thread.c | 12 +++++++++++- > 1 file changed, 11 insertions(+), 1 deletion(-) > > diff --git a/tools/perf/util/thread.c b/tools/perf/util/thread.c > index 873ab505ca80..590793cc5142 100644 > --- a/tools/perf/util/thread.c > +++ b/tools/perf/util/thread.c > @@ -214,14 +214,24 @@ struct comm *thread__comm(const struct thread *thread) > > struct comm *thread__exec_comm(const struct thread *thread) > { > - struct comm *comm, *last = NULL; > + struct comm *comm, *last = NULL, *second_last = NULL; > > list_for_each_entry(comm, &thread->comm_list, list) { > if (comm->exec) > return comm; > + second_last = last; > last = comm; > } > > + /* > + * 'last' with no start time might be the parent's comm of a synthesized > + * thread (created by processing a synthesized fork event). For a main > + * thread, that is very probably wrong. Prefer a later comm to avoid > + * that case. > + */ > + if (second_last && !last->start && thread->pid_ == thread->tid) > + return second_last; > + > return last; > } > > -- > 2.17.1 -- - Arnaldo
