| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <8c62094a-921c-2f3a-2130-3f083f4ac178@huawei.com>
Date: Mon, 31 Jul 2023 22:28:05 +0800
From: Yang Jihong <yangjihong1@...wei.com>
To: Adrian Hunter <adrian.hunter@...el.com>, <peterz@...radead.org>,
<mingo@...hat.com>, <acme@...nel.org>, <mark.rutland@....com>,
<alexander.shishkin@...ux.intel.com>, <jolsa@...nel.org>,
<namhyung@...nel.org>, <irogers@...gle.com>,
<kan.liang@...ux.intel.com>, <james.clark@....com>,
<tmricht@...ux.ibm.com>, <ak@...ux.intel.com>,
<anshuman.khandual@....com>, <linux-kernel@...r.kernel.org>,
<linux-perf-users@...r.kernel.org>
Subject: Re: [PATCH v3 4/7] perf record: Track sideband events for all CPUs
when tracing selected CPUs
Hello,
On 2023/7/31 21:01, Adrian Hunter wrote:
> On 31/07/23 15:38, Yang Jihong wrote:
>> Hello,
>>
>> On 2023/7/31 19:08, Adrian Hunter wrote:
>>> On 22/07/23 12:32, Yang Jihong wrote:
>>>> User space tasks can migrate between CPUs, we need to track side-band
>>>> events for all CPUs.
>>>>
>>>> The specific scenarios are as follows:
>>>>
>>>> CPU0 CPU1
>>>> perf record -C 0 start
>>>> taskA starts to be created and executed
>>>> -> PERF_RECORD_COMM and PERF_RECORD_MMAP
>>>> events only deliver to CPU1
>>>> ......
>>>> |
>>>> migrate to CPU0
>>>> |
>>>> Running on CPU0 <----------/
>>>> ...
>>>>
>>>> perf record -C 0 stop
>>>>
>>>> Now perf samples the PC of taskA. However, perf does not record the
>>>> PERF_RECORD_COMM and PERF_RECORD_MMAP events of taskA.
>>>> Therefore, the comm and symbols of taskA cannot be parsed.
>>>>
>>>> The solution is to record sideband events for all CPUs when tracing
>>>> selected CPUs. Because this modifies the default behavior, add related
>>>> comments to the perf record man page.
>>>>
>>>> The sys_perf_event_open invoked is as follows:
>>>>
>>>> # perf --debug verbose=3 record -e cpu-clock -C 1 true
>>>> <SNIP>
>>>> Opening: cpu-clock
>>>> ------------------------------------------------------------
>>>> perf_event_attr:
>>>> type 1 (PERF_TYPE_SOFTWARE)
>>>> size 136
>>>> config 0 (PERF_COUNT_SW_CPU_CLOCK)
>>>> { sample_period, sample_freq } 4000
>>>> sample_type IP|TID|TIME|CPU|PERIOD|IDENTIFIER
>>>> read_format ID|LOST
>>>> disabled 1
>>>> inherit 1
>>>> freq 1
>>>> sample_id_all 1
>>>> exclude_guest 1
>>>> ------------------------------------------------------------
>>>> sys_perf_event_open: pid -1 cpu 1 group_fd -1 flags 0x8 = 5
>>>> Opening: dummy:u
>>>> ------------------------------------------------------------
>>>> perf_event_attr:
>>>> type 1 (PERF_TYPE_SOFTWARE)
>>>> size 136
>>>> config 0x9 (PERF_COUNT_SW_DUMMY)
>>>> { sample_period, sample_freq } 1
>>>> sample_type IP|TID|TIME|CPU|IDENTIFIER
>>>> read_format ID|LOST
>>>> inherit 1
>>>> exclude_kernel 1
>>>> exclude_hv 1
>>>> mmap 1
>>>> comm 1
>>>> task 1
>>>> sample_id_all 1
>>>> exclude_guest 1
>>>> mmap2 1
>>>> comm_exec 1
>>>> ksymbol 1
>>>> bpf_event 1
>>>> ------------------------------------------------------------
>>>> sys_perf_event_open: pid -1 cpu 0 group_fd -1 flags 0x8 = 6
>>>> sys_perf_event_open: pid -1 cpu 1 group_fd -1 flags 0x8 = 7
>>>> sys_perf_event_open: pid -1 cpu 2 group_fd -1 flags 0x8 = 9
>>>> sys_perf_event_open: pid -1 cpu 3 group_fd -1 flags 0x8 = 10
>>>> sys_perf_event_open: pid -1 cpu 4 group_fd -1 flags 0x8 = 11
>>>> sys_perf_event_open: pid -1 cpu 5 group_fd -1 flags 0x8 = 12
>>>> sys_perf_event_open: pid -1 cpu 6 group_fd -1 flags 0x8 = 13
>>>> sys_perf_event_open: pid -1 cpu 7 group_fd -1 flags 0x8 = 14
>>>> <SNIP>
>>>>
>>>> Signed-off-by: Yang Jihong <yangjihong1@...wei.com>
>>>> ---
>>>> tools/perf/Documentation/perf-record.txt | 3 +++
>>>> tools/perf/builtin-record.c | 14 +++++++++++++-
>>>> 2 files changed, 16 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
>>>> index 680396c56bd1..dac53ece51ab 100644
>>>> --- a/tools/perf/Documentation/perf-record.txt
>>>> +++ b/tools/perf/Documentation/perf-record.txt
>>>> @@ -388,6 +388,9 @@ comma-separated list with no space: 0,1. Ranges of CPUs are specified with -: 0-
>>>> In per-thread mode with inheritance mode on (default), samples are captured only when
>>>> the thread executes on the designated CPUs. Default is to monitor all CPUs.
>>>> +User space tasks can migrate between CPUs, so when tracing selected CPUs,
>>>> +a dummy event is created to track sideband for all CPUs.
>>>> +
>>>> -B::
>>>> --no-buildid::
>>>> Do not save the build ids of binaries in the perf.data files. This skips
>>>> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
>>>> index 3ff9d972225e..4e8e97928f05 100644
>>>> --- a/tools/perf/builtin-record.c
>>>> +++ b/tools/perf/builtin-record.c
>>>> @@ -912,6 +912,7 @@ static int record__config_tracking_events(struct record *rec)
>>>> {
>>>> struct record_opts *opts = &rec->opts;
>>>> struct evlist *evlist = rec->evlist;
>>>> + bool system_wide = false;
>>>> struct evsel *evsel;
>>>> /*
>>>> @@ -921,7 +922,18 @@ static int record__config_tracking_events(struct record *rec)
>>>> */
>>>> if (opts->target.initial_delay || target__has_cpu(&opts->target) ||
>>>> perf_pmus__num_core_pmus() > 1) {
>>>> - evsel = evlist__findnew_tracking_event(evlist, false);
>>>> +
>>>> + /*
>>>> + * User space tasks can migrate between CPUs, so when tracing
>>>> + * selected CPUs, sideband for all CPUs is still needed.
>>>> + *
>>>> + * If all (non-dummy) evsel have exclude_user,
>>>> + * system_wide is not needed.
>>>> + */
>>>> + if (!!opts->target.cpu_list && !opts->all_kernel)
>>>
>>> Not everyone uses all-kernel. Can we check the evsels are either dummy
>>> or exclude_user?
>> For perf_record, exclude_user of all evsels is set in evsel__config(), and record__config_tracking_events() is before evsel__config().
>>
>> Uh..., it seems that only opts->all_kernel can be used to check exclude_user of evsels.
>>
>> void evsel__config()
>> {
>> ...
>> if (opts->all_kernel) {
>> attr->exclude_kernel = 0;
>> attr->exclude_user = 1;
>> }
>> ...
>> }
>
> The parser updates attr in accordance with ":k" etc. I guess
Yes, the ":k" situation also needs to be considered.
> opts->all_kernel or opts->all_user override that as well.
Yes, opts->all_kernel and opts->all_user will overwrite the original
attr, see [1].
may need to check all_user, all_kernel and non-dummy exclude_user at the
same time:
if ((all_user && one_non_dummy_exist) ||
(!all_user && !all_kernel && one_non_dummy_without_exclude_user)) {
system_wide = true;
}
[1]
# perf --debug verbose=2 record -e cpu-clock:u --all-kernel true
<SNIP>
------------------------------------------------------------
perf_event_attr:
type 1 (PERF_TYPE_SOFTWARE)
size 136
config 0 (PERF_COUNT_SW_CPU_CLOCK)
{ sample_period, sample_freq } 4000
sample_type IP|TID|TIME|PERIOD
read_format ID|LOST
disabled 1
inherit 1
exclude_user 1
exclude_hv 1
mmap 1
comm 1
freq 1
enable_on_exec 1
task 1
sample_id_all 1
exclude_guest 1
mmap2 1
comm_exec 1
ksymbol 1
bpf_event 1
------------------------------------------------------------
<SNIP>
Thanks,
Yang
Powered by blists - more mailing lists