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tracing: Rename stacktrace field to common_stacktrace

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The histogram and synthetic events can use a pseudo event called
"stacktrace" that will create a stacktrace at the time of the event and
use it just like it was a normal field. We have other pseudo events such
as "common_cpu" and "common_timestamp". To stay consistent with that,
convert "stacktrace" to "common_stacktrace". As this was used in older
kernels, to keep backward compatibility, this will act just like
"common_cpu" did with "cpu". That is, "cpu" will be the same as
"common_cpu" unless the event has a "cpu" field. In which case, the
event's field is used. The same is true with "stacktrace".

Also update the documentation to reflect this change.

Link: https://lore.kernel.org/linux-trace-kernel/20230523230913.6860e28d@rorschach.local.home

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Tom Zanussi <zanussi@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (Google) 2023-05-23 23:09:13 -04:00
parent e30fbc618e
commit 4b512860bd
5 changed files with 46 additions and 39 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

64
Documentation/trace/histogram.rst
View File

@ -35,7 +35,7 @@ Documentation written by Tom Zanussi
in place of an explicit value field - this is simply a count of
event hits. If 'values' isn't specified, an implicit 'hitcount'
value will be automatically created and used as the only value.
Keys can be any field, or the special string 'stacktrace', which
Keys can be any field, or the special string 'common_stacktrace', which
will use the event's kernel stacktrace as the key. The keywords
'keys' or 'key' can be used to specify keys, and the keywords
'values', 'vals', or 'val' can be used to specify values. Compound
@ -54,7 +54,7 @@ Documentation written by Tom Zanussi
'compatible' if the fields named in the trigger share the same
number and type of fields and those fields also have the same names.
Note that any two events always share the compatible 'hitcount' and
'stacktrace' fields and can therefore be combined using those
'common_stacktrace' fields and can therefore be combined using those
fields, however pointless that may be.
'hist' triggers add a 'hist' file to each event's subdirectory.
@ -547,9 +547,9 @@ Extended error information
the hist trigger display symbolic call_sites, we can have the hist
trigger additionally display the complete set of kernel stack traces
that led to each call_site. To do that, we simply use the special
value 'stacktrace' for the key parameter::
value 'common_stacktrace' for the key parameter::
# echo 'hist:keys=stacktrace:values=bytes_req,bytes_alloc:sort=bytes_alloc' > \
# echo 'hist:keys=common_stacktrace:values=bytes_req,bytes_alloc:sort=bytes_alloc' > \
/sys/kernel/tracing/events/kmem/kmalloc/trigger
The above trigger will use the kernel stack trace in effect when an
@ -561,9 +561,9 @@ Extended error information
every callpath to a kmalloc for a kernel compile)::
# cat /sys/kernel/tracing/events/kmem/kmalloc/hist
# trigger info: hist:keys=stacktrace:vals=bytes_req,bytes_alloc:sort=bytes_alloc:size=2048 [active]
# trigger info: hist:keys=common_stacktrace:vals=bytes_req,bytes_alloc:sort=bytes_alloc:size=2048 [active]
{ stacktrace:
{ common_stacktrace:
__kmalloc_track_caller+0x10b/0x1a0
kmemdup+0x20/0x50
hidraw_report_event+0x8a/0x120 [hid]
@ -581,7 +581,7 @@ Extended error information
cpu_startup_entry+0x315/0x3e0
rest_init+0x7c/0x80
} hitcount: 3 bytes_req: 21 bytes_alloc: 24
{ stacktrace:
{ common_stacktrace:
__kmalloc_track_caller+0x10b/0x1a0
kmemdup+0x20/0x50
hidraw_report_event+0x8a/0x120 [hid]
@ -596,7 +596,7 @@ Extended error information
do_IRQ+0x5a/0xf0
ret_from_intr+0x0/0x30
} hitcount: 3 bytes_req: 21 bytes_alloc: 24
{ stacktrace:
{ common_stacktrace:
kmem_cache_alloc_trace+0xeb/0x150
aa_alloc_task_context+0x27/0x40
apparmor_cred_prepare+0x1f/0x50
@ -608,7 +608,7 @@ Extended error information
.
.
.
{ stacktrace:
{ common_stacktrace:
__kmalloc+0x11b/0x1b0
i915_gem_execbuffer2+0x6c/0x2c0 [i915]
drm_ioctl+0x349/0x670 [drm]
@ -616,7 +616,7 @@ Extended error information
SyS_ioctl+0x81/0xa0
system_call_fastpath+0x12/0x6a
} hitcount: 17726 bytes_req: 13944120 bytes_alloc: 19593808
{ stacktrace:
{ common_stacktrace:
__kmalloc+0x11b/0x1b0
load_elf_phdrs+0x76/0xa0
load_elf_binary+0x102/0x1650
@ -625,7 +625,7 @@ Extended error information
SyS_execve+0x3a/0x50
return_from_execve+0x0/0x23
} hitcount: 33348 bytes_req: 17152128 bytes_alloc: 20226048
{ stacktrace:
{ common_stacktrace:
kmem_cache_alloc_trace+0xeb/0x150
apparmor_file_alloc_security+0x27/0x40
security_file_alloc+0x16/0x20
@ -636,7 +636,7 @@ Extended error information
SyS_open+0x1e/0x20
system_call_fastpath+0x12/0x6a
} hitcount: 4766422 bytes_req: 9532844 bytes_alloc: 38131376
{ stacktrace:
{ common_stacktrace:
__kmalloc+0x11b/0x1b0
seq_buf_alloc+0x1b/0x50
seq_read+0x2cc/0x370
@ -1026,7 +1026,7 @@ Extended error information
First we set up an initially paused stacktrace trigger on the
netif_receive_skb event::
# echo 'hist:key=stacktrace:vals=len:pause' > \
# echo 'hist:key=common_stacktrace:vals=len:pause' > \
/sys/kernel/tracing/events/net/netif_receive_skb/trigger
Next, we set up an 'enable_hist' trigger on the sched_process_exec
@ -1060,9 +1060,9 @@ Extended error information
$ wget https://www.kernel.org/pub/linux/kernel/v3.x/patch-3.19.xz
# cat /sys/kernel/tracing/events/net/netif_receive_skb/hist
# trigger info: hist:keys=stacktrace:vals=len:sort=hitcount:size=2048 [paused]
# trigger info: hist:keys=common_stacktrace:vals=len:sort=hitcount:size=2048 [paused]
{ stacktrace:
{ common_stacktrace:
__netif_receive_skb_core+0x46d/0x990
__netif_receive_skb+0x18/0x60
netif_receive_skb_internal+0x23/0x90
@ -1079,7 +1079,7 @@ Extended error information
kthread+0xd2/0xf0
ret_from_fork+0x42/0x70
} hitcount: 85 len: 28884
{ stacktrace:
{ common_stacktrace:
__netif_receive_skb_core+0x46d/0x990
__netif_receive_skb+0x18/0x60
netif_receive_skb_internal+0x23/0x90
@ -1097,7 +1097,7 @@ Extended error information
irq_thread+0x11f/0x150
kthread+0xd2/0xf0
} hitcount: 98 len: 664329
{ stacktrace:
{ common_stacktrace:
__netif_receive_skb_core+0x46d/0x990
__netif_receive_skb+0x18/0x60
process_backlog+0xa8/0x150
@ -1115,7 +1115,7 @@ Extended error information
inet_sendmsg+0x64/0xa0
sock_sendmsg+0x3d/0x50
} hitcount: 115 len: 13030
{ stacktrace:
{ common_stacktrace:
__netif_receive_skb_core+0x46d/0x990
__netif_receive_skb+0x18/0x60
netif_receive_skb_internal+0x23/0x90
@ -1142,14 +1142,14 @@ Extended error information
into the histogram. In order to avoid having to set everything up
again, we can just clear the histogram first::
# echo 'hist:key=stacktrace:vals=len:clear' >> \
# echo 'hist:key=common_stacktrace:vals=len:clear' >> \
/sys/kernel/tracing/events/net/netif_receive_skb/trigger
Just to verify that it is in fact cleared, here's what we now see in
the hist file::
# cat /sys/kernel/tracing/events/net/netif_receive_skb/hist
# trigger info: hist:keys=stacktrace:vals=len:sort=hitcount:size=2048 [paused]
# trigger info: hist:keys=common_stacktrace:vals=len:sort=hitcount:size=2048 [paused]
Totals:
Hits: 0
@ -1485,12 +1485,12 @@ Extended error information
And here's an example that shows how to combine histogram data from
any two events even if they don't share any 'compatible' fields
other than 'hitcount' and 'stacktrace'. These commands create a
other than 'hitcount' and 'common_stacktrace'. These commands create a
couple of triggers named 'bar' using those fields::
# echo 'hist:name=bar:key=stacktrace:val=hitcount' > \
# echo 'hist:name=bar:key=common_stacktrace:val=hitcount' > \
/sys/kernel/tracing/events/sched/sched_process_fork/trigger
# echo 'hist:name=bar:key=stacktrace:val=hitcount' > \
# echo 'hist:name=bar:key=common_stacktrace:val=hitcount' > \
/sys/kernel/tracing/events/net/netif_rx/trigger
And displaying the output of either shows some interesting if
@ -1501,16 +1501,16 @@ Extended error information
# event histogram
#
# trigger info: hist:name=bar:keys=stacktrace:vals=hitcount:sort=hitcount:size=2048 [active]
# trigger info: hist:name=bar:keys=common_stacktrace:vals=hitcount:sort=hitcount:size=2048 [active]
#
{ stacktrace:
{ common_stacktrace:
kernel_clone+0x18e/0x330
kernel_thread+0x29/0x30
kthreadd+0x154/0x1b0
ret_from_fork+0x3f/0x70
} hitcount: 1
{ stacktrace:
{ common_stacktrace:
netif_rx_internal+0xb2/0xd0
netif_rx_ni+0x20/0x70
dev_loopback_xmit+0xaa/0xd0
@ -1528,7 +1528,7 @@ Extended error information
call_cpuidle+0x3b/0x60
cpu_startup_entry+0x22d/0x310
} hitcount: 1
{ stacktrace:
{ common_stacktrace:
netif_rx_internal+0xb2/0xd0
netif_rx_ni+0x20/0x70
dev_loopback_xmit+0xaa/0xd0
@ -1543,7 +1543,7 @@ Extended error information
SyS_sendto+0xe/0x10
entry_SYSCALL_64_fastpath+0x12/0x6a
} hitcount: 2
{ stacktrace:
{ common_stacktrace:
netif_rx_internal+0xb2/0xd0
netif_rx+0x1c/0x60
loopback_xmit+0x6c/0xb0
@ -1561,7 +1561,7 @@ Extended error information
sock_sendmsg+0x38/0x50
___sys_sendmsg+0x14e/0x270
} hitcount: 76
{ stacktrace:
{ common_stacktrace:
netif_rx_internal+0xb2/0xd0
netif_rx+0x1c/0x60
loopback_xmit+0x6c/0xb0
@ -1579,7 +1579,7 @@ Extended error information
sock_sendmsg+0x38/0x50
___sys_sendmsg+0x269/0x270
} hitcount: 77
{ stacktrace:
{ common_stacktrace:
netif_rx_internal+0xb2/0xd0
netif_rx+0x1c/0x60
loopback_xmit+0x6c/0xb0
@ -1597,7 +1597,7 @@ Extended error information
sock_sendmsg+0x38/0x50
SYSC_sendto+0xef/0x170
} hitcount: 88
{ stacktrace:
{ common_stacktrace:
kernel_clone+0x18e/0x330
SyS_clone+0x19/0x20
entry_SYSCALL_64_fastpath+0x12/0x6a
@ -1949,7 +1949,7 @@ uninterruptible state::
# cd /sys/kernel/tracing
# echo 's:block_lat pid_t pid; u64 delta; unsigned long[] stack;' > dynamic_events
# echo 'hist:keys=next_pid:ts=common_timestamp.usecs,st=stacktrace if prev_state == 2' >> events/sched/sched_switch/trigger
# echo 'hist:keys=next_pid:ts=common_timestamp.usecs,st=common_stacktrace if prev_state == 2' >> events/sched/sched_switch/trigger
# echo 'hist:keys=prev_pid:delta=common_timestamp.usecs-$ts,s=$st:onmax($delta).trace(block_lat,prev_pid,$delta,$s)' >> events/sched/sched_switch/trigger
# echo 1 > events/synthetic/block_lat/enable
# cat trace

1
include/linux/trace_events.h
View File

@ -806,6 +806,7 @@ enum {
FILTER_TRACE_FN,
FILTER_COMM,
FILTER_CPU,
FILTER_STACKTRACE,
};
extern int trace_event_raw_init(struct trace_event_call *call);

2
kernel/trace/trace.c
View File

@ -5752,7 +5752,7 @@ static const char readme_msg[] =
"\t table using the key(s) and value(s) named, and the value of a\n"
"\t sum called 'hitcount' is incremented. Keys and values\n"
"\t correspond to fields in the event's format description. Keys\n"
"\t can be any field, or the special string 'stacktrace'.\n"
"\t can be any field, or the special string 'common_stacktrace'.\n"
"\t Compound keys consisting of up to two fields can be specified\n"
"\t by the 'keys' keyword. Values must correspond to numeric\n"
"\t fields. Sort keys consisting of up to two fields can be\n"

2
kernel/trace/trace_events.c
View File

@ -194,6 +194,8 @@ static int trace_define_generic_fields(void)
__generic_field(int, common_cpu, FILTER_CPU);
__generic_field(char *, COMM, FILTER_COMM);
__generic_field(char *, comm, FILTER_COMM);
__generic_field(char *, stacktrace, FILTER_STACKTRACE);
__generic_field(char *, STACKTRACE, FILTER_STACKTRACE);
return ret;
}

16
kernel/trace/trace_events_hist.c
View File

@ -1364,7 +1364,7 @@ static const char *hist_field_name(struct hist_field *field,
if (field->field)
field_name = field->field->name;
else
field_name = "stacktrace";
field_name = "common_stacktrace";
} else if (field->flags & HIST_FIELD_FL_HITCOUNT)
field_name = "hitcount";
@ -2367,7 +2367,7 @@ parse_field(struct hist_trigger_data *hist_data, struct trace_event_file *file,
hist_data->enable_timestamps = true;
if (*flags & HIST_FIELD_FL_TIMESTAMP_USECS)
hist_data->attrs->ts_in_usecs = true;
} else if (strcmp(field_name, "stacktrace") == 0) {
} else if (strcmp(field_name, "common_stacktrace") == 0) {
*flags |= HIST_FIELD_FL_STACKTRACE;
} else if (strcmp(field_name, "common_cpu") == 0)
*flags |= HIST_FIELD_FL_CPU;
@ -2378,11 +2378,15 @@ parse_field(struct hist_trigger_data *hist_data, struct trace_event_file *file,
if (!field || !field->size) {
/*
* For backward compatibility, if field_name
* was "cpu", then we treat this the same as
* common_cpu. This also works for "CPU".
* was "cpu" or "stacktrace", then we treat this
* the same as common_cpu and common_stacktrace
* respectively. This also works for "CPU", and
* "STACKTRACE".
*/
if (field && field->filter_type == FILTER_CPU) {
*flags |= HIST_FIELD_FL_CPU;
} else if (field && field->filter_type == FILTER_STACKTRACE) {
*flags |= HIST_FIELD_FL_STACKTRACE;
} else {
hist_err(tr, HIST_ERR_FIELD_NOT_FOUND,
errpos(field_name));
@ -5394,7 +5398,7 @@ static void hist_trigger_print_key(struct seq_file *m,
if (key_field->field)
seq_printf(m, "%s.stacktrace", key_field->field->name);
else
seq_puts(m, "stacktrace:\n");
seq_puts(m, "common_stacktrace:\n");
hist_trigger_stacktrace_print(m,
key + key_field->offset,
HIST_STACKTRACE_DEPTH);
@ -5977,7 +5981,7 @@ static int event_hist_trigger_print(struct seq_file *m,
if (field->field)
seq_printf(m, "%s.stacktrace", field->field->name);
else
seq_puts(m, "stacktrace");
seq_puts(m, "common_stacktrace");
} else
hist_field_print(m, field);
}