From: Adrian Hunter <adrian.hunter@intel.com>
To: Ian Rogers <irogers@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Jiri Olsa <jolsa@kernel.org>, Namhyung Kim <namhyung@kernel.org>,
Nick Terrell <terrelln@fb.com>,
Kan Liang <kan.liang@linux.intel.com>, Song Liu <song@kernel.org>,
Sandipan Das <sandipan.das@amd.com>,
Anshuman Khandual <anshuman.khandual@arm.com>,
James Clark <james.clark@arm.com>,
Liam Howlett <liam.howlett@oracle.com>,
Miguel Ojeda <ojeda@kernel.org>, Leo Yan <leo.yan@linaro.org>,
German Gomez <german.gomez@arm.com>,
Ravi Bangoria <ravi.bangoria@amd.com>,
Artem Savkov <asavkov@redhat.com>,
Athira Rajeev <atrajeev@linux.vnet.ibm.com>,
Andi Kleen <ak@linux.intel.com>,
linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org,
bpf@vger.kernel.org
Subject: Re: [PATCH v2 13/13] perf machine thread: Remove exited threads by default
Date: Tue, 24 Oct 2023 08:19:23 +0300 [thread overview]
Message-ID: <92fe21ab-af6f-4417-b241-eac0532e115a@intel.com> (raw)
In-Reply-To: <CAP-5=fX303b8-hQXWaRibtYFyBS2sQywDSKR6KhKMUMX_0gzrw@mail.gmail.com>
On 23/10/23 21:49, Ian Rogers wrote:
> On Mon, Oct 23, 2023 at 7:24 AM Adrian Hunter <adrian.hunter@intel.com> wrote:
>>
>> On 12/10/23 09:23, Ian Rogers wrote:
>>> struct thread values hold onto references to mmaps, dsos, etc. When a
>>> thread exits it is necessary to clean all of this memory up by
>>> removing the thread from the machine's threads. Some tools require
>>> this doesn't happen, such as perf report if offcpu events exist or if
>>> a task list is being generated, so add a symbol_conf value to make the
>>> behavior optional. When an exited thread is left in the machine's
>>> threads, mark it as exited.
>>>
>>> This change relates to commit 40826c45eb0b ("perf thread: Remove
>>> notion of dead threads"). Dead threads were removed as they had a
>>> reference count of 0 and were difficult to reason about with the
>>> reference count checker. Here a thread is removed from threads when it
>>> exits, unless via symbol_conf the exited thread isn't remove and is
>>> marked as exited. Reference counting behaves as it normally does.
>>
>> Can we exclude AUX area tracing?
>>
>> Essentially, the EXIT event happens when the task is still running
>> in kernel mode, so the thread has not in fact fully exited.
>>
>> Example:
>>
>> # perf record -a --kcore -e intel_pt// uname
>>
>> Before:
>>
>> # perf script --itrace=b --show-task-events -C6 | grep -C10 EXIT
>> uname 14740 [006] 26795.092638: 1 branches: ffffffffb63124ee __perf_event_header__init_id+0x5e ([kernel.kallsyms]) => ffffffffb63124f7 __perf_event_header__init_id+0x67 ([kernel.kallsyms])
>> uname 14740 [006] 26795.092638: 1 branches: ffffffffb6312501 __perf_event_header__init_id+0x71 ([kernel.kallsyms]) => ffffffffb6312512 __perf_event_header__init_id+0x82 ([kernel.kallsyms])
>> uname 14740 [006] 26795.092638: 1 branches: ffffffffb6312531 __perf_event_header__init_id+0xa1 ([kernel.kallsyms]) => ffffffffb6316b3a perf_event_task_output+0x26a ([kernel.kallsyms])
>> uname 14740 [006] 26795.092638: 1 branches: ffffffffb6316b40 perf_event_task_output+0x270 ([kernel.kallsyms]) => ffffffffb6316959 perf_event_task_output+0x89 ([kernel.kallsyms])
>> uname 14740 [006] 26795.092638: 1 branches: ffffffffb6316966 perf_event_task_output+0x96 ([kernel.kallsyms]) => ffffffffb6322040 perf_output_begin+0x0 ([kernel.kallsyms])
>> uname 14740 [006] 26795.092638: 1 branches: ffffffffb6322080 perf_output_begin+0x40 ([kernel.kallsyms]) => ffffffffb6194dc0 __rcu_read_lock+0x0 ([kernel.kallsyms])
>> uname 14740 [006] 26795.092638: 1 branches: ffffffffb6194de1 __rcu_read_lock+0x21 ([kernel.kallsyms]) => ffffffffb6322085 perf_output_begin+0x45 ([kernel.kallsyms])
>> uname 14740 [006] 26795.092638: 1 branches: ffffffffb63220ce perf_output_begin+0x8e ([kernel.kallsyms]) => ffffffffb611d280 preempt_count_add+0x0 ([kernel.kallsyms])
>> uname 14740 [006] 26795.092638: 1 branches: ffffffffb611d2bf preempt_count_add+0x3f ([kernel.kallsyms]) => ffffffffb63220d3 perf_output_begin+0x93 ([kernel.kallsyms])
>> uname 14740 [006] 26795.092638: 1 branches: ffffffffb63220e8 perf_output_begin+0xa8 ([kernel.kallsyms]) => ffffffffb63220ff perf_output_begin+0xbf ([kernel.kallsyms])
>> uname 14740 [006] 26795.092638: PERF_RECORD_EXIT(14740:14740):(14739:14739)
>> uname 14740 [006] 26795.092638: 1 branches: ffffffffb6322119 perf_output_begin+0xd9 ([kernel.kallsyms]) => ffffffffb6322128 perf_output_begin+0xe8 ([kernel.kallsyms])
>> uname 14740 [006] 26795.092638: 1 branches: ffffffffb6322146 perf_output_begin+0x106 ([kernel.kallsyms]) => ffffffffb63220ea perf_output_begin+0xaa ([kernel.kallsyms])
>> uname 14740 [006] 26795.092638: 1 branches: ffffffffb63220f9 perf_output_begin+0xb9 ([kernel.kallsyms]) => ffffffffb63221ab perf_output_begin+0x16b ([kernel.kallsyms])
>> uname 14740 [006] 26795.092638: 1 branches: ffffffffb63221ae perf_output_begin+0x16e ([kernel.kallsyms]) => ffffffffb63221b6 perf_output_begin+0x176 ([kernel.kallsyms])
>> uname 14740 [006] 26795.092638: 1 branches: ffffffffb6322202 perf_output_begin+0x1c2 ([kernel.kallsyms]) => ffffffffb6322167 perf_output_begin+0x127 ([kernel.kallsyms])
>> uname 14740 [006] 26795.092638: 1 branches: ffffffffb632218c perf_output_begin+0x14c ([kernel.kallsyms]) => ffffffffb631696b perf_event_task_output+0x9b ([kernel.kallsyms])
>> uname 14740 [006] 26795.092638: 1 branches: ffffffffb6316990 perf_event_task_output+0xc0 ([kernel.kallsyms]) => ffffffffb61034a0 __task_pid_nr_ns+0x0 ([kernel.kallsyms])
>> uname 14740 [006] 26795.092638: 1 branches: ffffffffb61034b7 __task_pid_nr_ns+0x17 ([kernel.kallsyms]) => ffffffffb6194dc0 __rcu_read_lock+0x0 ([kernel.kallsyms])
>> uname 14740 [006] 26795.092638: 1 branches: ffffffffb6194de1 __rcu_read_lock+0x21 ([kernel.kallsyms]) => ffffffffb61034bc __task_pid_nr_ns+0x1c ([kernel.kallsyms])
>> uname 14740 [006] 26795.092638: 1 branches: ffffffffb6103503 __task_pid_nr_ns+0x63 ([kernel.kallsyms]) => ffffffffb610353b __task_pid_nr_ns+0x9b ([kernel.kallsyms])
>>
>> After:
>>
>> $ perf script --itrace=b --show-task-events -C6 | grep -C10 EXIT
>> uname 14740 [006] 26795.092638: 1 branches: ffffffffb63124ee __perf_event_header__init_id+0x5e ([kernel.kallsyms]) => ffffffffb63124f7 __perf_event_header__init_id+0x67 ([kernel.kallsyms])
>> uname 14740 [006] 26795.092638: 1 branches: ffffffffb6312501 __perf_event_header__init_id+0x71 ([kernel.kallsyms]) => ffffffffb6312512 __perf_event_header__init_id+0x82 ([kernel.kallsyms])
>> uname 14740 [006] 26795.092638: 1 branches: ffffffffb6312531 __perf_event_header__init_id+0xa1 ([kernel.kallsyms]) => ffffffffb6316b3a perf_event_task_output+0x26a ([kernel.kallsyms])
>> uname 14740 [006] 26795.092638: 1 branches: ffffffffb6316b40 perf_event_task_output+0x270 ([kernel.kallsyms]) => ffffffffb6316959 perf_event_task_output+0x89 ([kernel.kallsyms])
>> uname 14740 [006] 26795.092638: 1 branches: ffffffffb6316966 perf_event_task_output+0x96 ([kernel.kallsyms]) => ffffffffb6322040 perf_output_begin+0x0 ([kernel.kallsyms])
>> uname 14740 [006] 26795.092638: 1 branches: ffffffffb6322080 perf_output_begin+0x40 ([kernel.kallsyms]) => ffffffffb6194dc0 __rcu_read_lock+0x0 ([kernel.kallsyms])
>> uname 14740 [006] 26795.092638: 1 branches: ffffffffb6194de1 __rcu_read_lock+0x21 ([kernel.kallsyms]) => ffffffffb6322085 perf_output_begin+0x45 ([kernel.kallsyms])
>> uname 14740 [006] 26795.092638: 1 branches: ffffffffb63220ce perf_output_begin+0x8e ([kernel.kallsyms]) => ffffffffb611d280 preempt_count_add+0x0 ([kernel.kallsyms])
>> uname 14740 [006] 26795.092638: 1 branches: ffffffffb611d2bf preempt_count_add+0x3f ([kernel.kallsyms]) => ffffffffb63220d3 perf_output_begin+0x93 ([kernel.kallsyms])
>> uname 14740 [006] 26795.092638: 1 branches: ffffffffb63220e8 perf_output_begin+0xa8 ([kernel.kallsyms]) => ffffffffb63220ff perf_output_begin+0xbf ([kernel.kallsyms])
>> uname 14740 [006] 26795.092638: PERF_RECORD_EXIT(14740:14740):(14739:14739)
>> :14740 14740 [006] 26795.092638: 1 branches: ffffffffb6322119 perf_output_begin+0xd9 ([kernel.kallsyms]) => ffffffffb6322128 perf_output_begin+0xe8 ([kernel.kallsyms])
>> :14740 14740 [006] 26795.092638: 1 branches: ffffffffb6322146 perf_output_begin+0x106 ([kernel.kallsyms]) => ffffffffb63220ea perf_output_begin+0xaa ([kernel.kallsyms])
>> :14740 14740 [006] 26795.092638: 1 branches: ffffffffb63220f9 perf_output_begin+0xb9 ([kernel.kallsyms]) => ffffffffb63221ab perf_output_begin+0x16b ([kernel.kallsyms])
>> :14740 14740 [006] 26795.092638: 1 branches: ffffffffb63221ae perf_output_begin+0x16e ([kernel.kallsyms]) => ffffffffb63221b6 perf_output_begin+0x176 ([kernel.kallsyms])
>> :14740 14740 [006] 26795.092638: 1 branches: ffffffffb6322202 perf_output_begin+0x1c2 ([kernel.kallsyms]) => ffffffffb6322167 perf_output_begin+0x127 ([kernel.kallsyms])
>> :14740 14740 [006] 26795.092638: 1 branches: ffffffffb632218c perf_output_begin+0x14c ([kernel.kallsyms]) => ffffffffb631696b perf_event_task_output+0x9b ([kernel.kallsyms])
>> :14740 14740 [006] 26795.092638: 1 branches: ffffffffb6316990 perf_event_task_output+0xc0 ([kernel.kallsyms]) => ffffffffb61034a0 __task_pid_nr_ns+0x0 ([kernel.kallsyms])
>> :14740 14740 [006] 26795.092638: 1 branches: ffffffffb61034b7 __task_pid_nr_ns+0x17 ([kernel.kallsyms]) => ffffffffb6194dc0 __rcu_read_lock+0x0 ([kernel.kallsyms])
>> :14740 14740 [006] 26795.092638: 1 branches: ffffffffb6194de1 __rcu_read_lock+0x21 ([kernel.kallsyms]) => ffffffffb61034bc __task_pid_nr_ns+0x1c ([kernel.kallsyms])
>> :14740 14740 [006] 26795.092638: 1 branches: ffffffffb6103503 __task_pid_nr_ns+0x63 ([kernel.kallsyms]) => ffffffffb610353b __task_pid_nr_ns+0x9b ([kernel.kallsyms])
>>
>> This will also affect samples made after PERF_RECORD_EXIT but before
>> the task finishes exiting.
>
> Makes sense. Would an appropriate fix be in perf_session__open to set:
> symbol_conf.keep_exited_threads = true;
>
> when:
> perf_header__has_feat(&session->header, HEADER_AUXTRACE)
>
> It is kind of hacky to be changing global state this way, but
> symbol_conf is like that in general.
That should work. Alternatively, could be added to
perf_event__process_auxtrace_info() which would tie it
more directly to auxtrace, and wouldn't have to check
HEADER_AUXTRACE.
prev parent reply other threads:[~2023-10-24 5:19 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-12 6:23 [PATCH v2 00/13] Improvements to memory use Ian Rogers
2023-10-12 6:23 ` [PATCH v2 01/13] perf machine: Avoid out of bounds LBR memory read Ian Rogers
2023-10-12 6:23 ` [PATCH v2 02/13] libperf rc_check: Make implicit enabling work for GCC Ian Rogers
2023-10-12 6:23 ` [PATCH v2 03/13] perf hist: Add missing puts to hist__account_cycles Ian Rogers
2023-10-18 23:16 ` Namhyung Kim
2023-10-24 16:12 ` Ian Rogers
2023-10-12 6:23 ` [PATCH v2 04/13] perf threads: Remove unused dead thread list Ian Rogers
2023-10-12 6:23 ` [PATCH v2 05/13] perf offcpu: Add missed btf_free Ian Rogers
2023-10-12 6:23 ` [PATCH v2 06/13] perf callchain: Make display use of branch_type_stat const Ian Rogers
2023-10-12 6:23 ` [PATCH v2 07/13] perf callchain: Make brtype_stat in callchain_list optional Ian Rogers
2023-10-12 6:23 ` [PATCH v2 08/13] perf callchain: Minor layout changes to callchain_list Ian Rogers
2023-10-12 6:23 ` [PATCH v2 09/13] perf mem_info: Add and use map_symbol__exit and addr_map_symbol__exit Ian Rogers
2023-10-18 23:20 ` Namhyung Kim
2023-10-24 20:52 ` Ian Rogers
2023-10-12 6:23 ` [PATCH v2 10/13] perf record: Lazy load kernel symbols Ian Rogers
2023-10-19 11:02 ` Adrian Hunter
2023-10-24 18:42 ` Ian Rogers
2023-10-12 6:23 ` [PATCH v2 11/13] libperf: Lazily allocate mmap event copy Ian Rogers
2023-10-12 6:23 ` [PATCH v2 12/13] perf mmap: Lazily initialize zstd streams Ian Rogers
2023-10-18 23:21 ` Namhyung Kim
2023-10-24 19:21 ` Ian Rogers
2023-10-12 6:23 ` [PATCH v2 13/13] perf machine thread: Remove exited threads by default Ian Rogers
2023-10-18 23:30 ` Namhyung Kim
2023-10-19 0:39 ` Ian Rogers
2023-10-20 21:08 ` Namhyung Kim
2023-10-23 14:24 ` Adrian Hunter
2023-10-23 18:49 ` Ian Rogers
2023-10-24 5:19 ` Adrian Hunter [this message]
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