On 05/01/2015 11:23 AM, Daniel Wagner wrote:
> On 05/01/2015 02:54 AM, Steven Rostedt wrote:
>> On Thu, 30 Apr 2015 21:14:52 -0500
>> Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx> wrote:
>>
>>
>>>> 'hist:key=latency.bucket:val=hitcount:sort=latency if cpu==0'
>>>>
>>>> but I haven't got this working. I didn't spend much time figuring out
>>>> why this doesn't work. Even if the above is working you still
>>>
>>> I think it doesn't work because the tracepoint doesn't actually have a
>>> 'cpu' field to use in the filter...
>>
>> Perhaps we should add special fields that don't use the tracepoint
>> field, but can use generically know fields that are always known when
>> the tracepoint is triggered. COMM could be one, as well as CPU.
Here a first attempt:
>From fcd910836179dd738b3300dbf93a30f352e90996 Mon Sep 17 00:00:00 2001
From: Daniel Wagner <daniel.wagner@xxxxxxxxxxxx>
Date: Mon, 4 May 2015 15:44:24 +0200
Subject: [PATCH] tracing: Allow triggers to filter for CPUs
By extending the filter rules by more 'generically know' fields
we can write triggers filters like
'stacktrace:5 if cpu == 1'
We add a new element to ftrace_common_fields which describes
the new 'generically know' field. This change is visiable to user space.
E.g. the format file changes for kmem:kmalloc changes to
name: kmalloc
ID: 395
format:
field:int cpu; offset:0; size:0; signed:1;
field:unsigned short common_type; offset:0; size:2; signed:0;
field:unsigned char common_flags; offset:2; size:1; signed:0;
field:unsigned char common_preempt_count; offset:3; size:1; signed:0;
field:int common_pid; offset:4; size:4; signed:1;
field:unsigned long call_site; offset:8; size:8; signed:0;
field:const void * ptr; offset:16; size:8; signed:0;
field:size_t bytes_req; offset:24; size:8; signed:0;
field:size_t bytes_alloc; offset:32; size:8; signed:0;
field:gfp_t gfp_flags; offset:40; size:4; signed:0;
I think that is not complete correct since the field cpu doesn't
really exists in trace event entry. Propably moving those known fields
their own list is a way to overcome this problem. What do you think?
And yes, I am still marveling on this comment
/* If not of not match is equal to not of not, then it is a match */
from DEFINE_COMPARISON_PRED. This led me to copy it for
filter_pred_cpu() :)
Not for inclusion!
Not-Signed-off-by: Daniel Wagner <daniel.wagner@xxxxxxxxxxxx>
---
kernel/trace/trace_events.c | 8 ++++++++
kernel/trace/trace_events_filter.c | 37 ++++++++++++++++++++++++++++++++++++-
2 files changed, 44 insertions(+), 1 deletion(-)
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index c4de47f..3f51f2b 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -144,6 +144,13 @@ int trace_define_field(struct ftrace_event_call *call, const char *type,
}
EXPORT_SYMBOL_GPL(trace_define_field);
+#define __trace_field(type, item) \
+ ret = __trace_define_field(&ftrace_common_fields, #type, \
+ #item, 0, 0, is_signed_type(type), \
+ FILTER_OTHER); \
+ if (ret) \
+ return ret;
+
#define __common_field(type, item) \
ret = __trace_define_field(&ftrace_common_fields, #type, \
"common_" #item, \
@@ -158,6 +165,7 @@ static int trace_define_common_fields(void)
int ret;
struct trace_entry ent;
+ __trace_field(int, cpu);
__common_field(unsigned short, type);
__common_field(unsigned char, flags);
__common_field(unsigned char, preempt_count);
diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index ced69da..af2a6bb 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -252,6 +252,38 @@ static int filter_pred_strloc(struct filter_pred *pred, void *event)
return match;
}
+/* Filter predicate for CPUs. */
+static int filter_pred_cpu(struct filter_pred *pred, void *event)
+{
+ int cpu, cmp;
+ int match = 0;
+
+ cpu = raw_smp_processor_id();
+ cmp = pred->val;
+
+ switch (pred->op) {
+ case OP_EQ:
+ match = cpu == cmp;
+ break;
+ case OP_LT:
+ match = cpu < cmp;
+ break;
+ case OP_LE:
+ match = cpu <= cmp;
+ break;
+ case OP_GT:
+ match = cpu > cmp;
+ break;
+ case OP_GE:
+ match = cpu >= cmp;
+ break;
+ default:
+ break;
+ }
+
+ return !!match == !pred->not;
+}
+
static int filter_pred_none(struct filter_pred *pred, void *event)
{
return 0;
@@ -1025,7 +1057,10 @@ static int init_pred(struct filter_parse_state *ps,
}
pred->val = val;
- fn = select_comparison_fn(pred->op, field->size,
+ if (!strcmp(field->name, "cpu"))
+ fn = filter_pred_cpu;
+ else
+ fn = select_comparison_fn(pred->op, field->size,
field->is_signed);
if (!fn) {
parse_error(ps, FILT_ERR_INVALID_OP, 0);
--
2.1.0
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