linux-kernel - Re: [PATCH v2] perf trace: Fix missing handling of --call-graph dwarf

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Message-Id: <4ead78ee-398b-c782-330f-61359ad40fe2@linux.vnet.ibm.com>
Date:   Mon, 15 Jan 2018 15:50:15 +0100
From:   Thomas-Mich Richter <tmricht@...ux.vnet.ibm.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
Cc:     linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        brueckner@...ux.vnet.ibm.com, schwidefsky@...ibm.com,
        heiko.carstens@...ibm.com
Subject: Re: [PATCH v2] perf trace: Fix missing handling of --call-graph dwarf

On 01/15/2018 03:16 PM, Arnaldo Carvalho de Melo wrote:
> Em Mon, Jan 15, 2018 at 10:57:52AM -0300, Arnaldo Carvalho de Melo escreveu:
>>> [root@f27 perf]# ./perf trace --no-syscalls --max-stack 4
>>>         -e probe_libc:inet_pton/call-graph=dwarf/ ping -6 -c 1 ::1
>>> PING ::1(::1) 56 data bytes
>>> 64 bytes from ::1: icmp_seq=1 ttl=64 time=0.020 ms
>>>
>>> --- ::1 ping statistics ---
>>> 1 packets transmitted, 1 received, 0% packet loss, time 0ms
>>> rtt min/avg/max/mdev = 0.020/0.020/0.020/0.000 ms
>>>      0.000 probe_libc:inet_pton:(7ffbc5f768a0))
>>>             __inet_pton (inlined)
>>>             gaih_inet.constprop.7 (/usr/lib64/libc-2.26.so)
>>>             __GI_getaddrinfo (inlined)
>>>             main (/usr/bin/ping)
>>> [root@f27 perf]#
>>>
>>>
>>> --> Dwarf call graph and --max-stack 4 is also honoured.
>>
>> [root@...et ~]# perf trace --no-syscalls -e probe_libc:inet_pton/call-graph=dwarf,max-stack=4/
>> perf trace --no-syscalls --max-stack 4 -e probe_libc:inet_pton/call-graph=dwarf/ ping -6 -c 1 ::1
>> Value too large for defined data type
>> [root@...et ~]# 
>>
>> Grrr.
> 
> 
> Got this one fixed with the following patch:
> 
> commit b78278e11f6992ca348a4b96aad3b2c0a9ecf0f0

[...]

> 
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index efa2e629a669..8f971a2301d1 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -731,14 +731,14 @@ static void apply_config_terms(struct perf_evsel *evsel,
>  	struct perf_evsel_config_term *term;
>  	struct list_head *config_terms = &evsel->config_terms;
>  	struct perf_event_attr *attr = &evsel->attr;
> -	struct callchain_param param;
> +	/* callgraph default */
> +	struct callchain_param param = {
> +		.record_mode = callchain_param.record_mode,
> +	};
>  	u32 dump_size = 0;
>  	int max_stack = 0;
>  	const char *callgraph_buf = NULL;
> 
> -	/* callgraph default */
> -	param.record_mode = callchain_param.record_mode;
> -
>  	list_for_each_entry(term, config_terms, list) {
>  		switch (term->type) {
>  		case PERF_EVSEL__CONFIG_TERM_PERIOD:

This patch works for me.
Here is the output on my s390x:

[root@...60047 perf]# ./perf trace --no-syscalls --max-stack 4 
	-e probe_libc:inet_pton/call-graph=dwarf/ ping -6 -c 1 ::1
PING ::1(::1) 56 data bytes
64 bytes from ::1: icmp_seq=1 ttl=64 time=0.070 ms

--- ::1 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.070/0.070/0.070/0.000 ms
     0.000 probe_libc:inet_pton:(3ffa70c2060))
           __GI___inet_pton (/usr/lib64/libc-2.26.so)
           gaih_inet (inlined)
           __GI_getaddrinfo (inlined)
           main (/usr/bin/ping)
[root@...60047 perf]# ./perf trace --no-syscalls --call-graph dwarf 
	-e probe_libc:inet_pton -- ping -6 -c 1 ::1
PING ::1(::1) 56 data bytes
64 bytes from ::1: icmp_seq=1 ttl=64 time=0.086 ms

--- ::1 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.086/0.086/0.086/0.000 ms
     0.000 probe_libc:inet_pton:(3ff93fc2060))
           __GI___inet_pton (/usr/lib64/libc-2.26.so)
           gaih_inet (inlined)
           __GI_getaddrinfo (inlined)
           main (/usr/bin/ping)
           __libc_start_main (/usr/lib64/libc-2.26.so)
           _start (/usr/bin/ping)
[root@...60047 perf]#

[root@...60047 perf]# ./perf trace --no-syscalls 
	-e probe_libc:inet_pton/call-graph=dwarf,max-stack=3/ ping -6 -c 1 ::1
PING ::1(::1) 56 data bytes
64 bytes from ::1: icmp_seq=1 ttl=64 time=0.066 ms

--- ::1 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.066/0.066/0.066/0.000 ms
     0.000 probe_libc:inet_pton:(3ffb82c2060))
           __GI___inet_pton (/usr/lib64/libc-2.26.so)
           gaih_inet (inlined)
           __GI_getaddrinfo (inlined)
           main (/usr/bin/ping)
           __libc_start_main (/usr/lib64/libc-2.26.so)
           _start (/usr/bin/ping)
[root@...60047 perf]# 

Not sure if this can work at all. Since dwarf stack unwinding is done in user space
the attr.sample_max_stack set to 3 is useless in this case.

Yout have my Tested-by.
-- 
Thomas Richter, Dept 3303, IBM LTC Boeblingen Germany
--
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