diff options
| -rw-r--r-- | Documentation/trace/ftrace.rst | 38 | ||||
| -rw-r--r-- | kernel/trace/ftrace.c | 30 | ||||
| -rw-r--r-- | kernel/trace/trace.h | 1 | ||||
| -rw-r--r-- | kernel/trace/trace_events_filter.c | 5 |
4 files changed, 74 insertions, 0 deletions
diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst index 6ce2763a2a3e..7c5e6d6ab5d1 100644 --- a/Documentation/trace/ftrace.rst +++ b/Documentation/trace/ftrace.rst @@ -233,6 +233,12 @@ of ftrace. Here is a list of some of the key files: This interface also allows for commands to be used. See the "Filter commands" section for more details. + As a speed up, since processing strings can't be quite expensive + and requires a check of all functions registered to tracing, instead + an index can be written into this file. A number (starting with "1") + written will instead select the same corresponding at the line position + of the "available_filter_functions" file. + set_ftrace_notrace: This has an effect opposite to that of @@ -2835,6 +2841,38 @@ Produces:: We can see that there's no more lock or preempt tracing. +Selecting function filters via index +------------------------------------ + +Because processing of strings is expensive (the address of the function +needs to be looked up before comparing to the string being passed in), +an index can be used as well to enable functions. This is useful in the +case of setting thousands of specific functions at a time. By passing +in a list of numbers, no string processing will occur. Instead, the function +at the specific location in the internal array (which corresponds to the +functions in the "available_filter_functions" file), is selected. + +:: + + # echo 1 > set_ftrace_filter + +Will select the first function listed in "available_filter_functions" + +:: + + # head -1 available_filter_functions + trace_initcall_finish_cb + + # cat set_ftrace_filter + trace_initcall_finish_cb + + # head -50 available_filter_functions | tail -1 + x86_pmu_commit_txn + + # echo 1 50 > set_ftrace_filter + # cat set_ftrace_filter + trace_initcall_finish_cb + x86_pmu_commit_txn Dynamic ftrace with the function graph tracer --------------------------------------------- diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index aac7847c0214..fa79323331b2 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -3702,6 +3702,31 @@ enter_record(struct ftrace_hash *hash, struct dyn_ftrace *rec, int clear_filter) } static int +add_rec_by_index(struct ftrace_hash *hash, struct ftrace_glob *func_g, + int clear_filter) +{ + long index = simple_strtoul(func_g->search, NULL, 0); + struct ftrace_page *pg; + struct dyn_ftrace *rec; + + /* The index starts at 1 */ + if (--index < 0) + return 0; + + do_for_each_ftrace_rec(pg, rec) { + if (pg->index <= index) { + index -= pg->index; + /* this is a double loop, break goes to the next page */ + break; + } + rec = &pg->records[index]; + enter_record(hash, rec, clear_filter); + return 1; + } while_for_each_ftrace_rec(); + return 0; +} + +static int ftrace_match_record(struct dyn_ftrace *rec, struct ftrace_glob *func_g, struct ftrace_glob *mod_g, int exclude_mod) { @@ -3769,6 +3794,11 @@ match_records(struct ftrace_hash *hash, char *func, int len, char *mod) if (unlikely(ftrace_disabled)) goto out_unlock; + if (func_g.type == MATCH_INDEX) { + found = add_rec_by_index(hash, &func_g, clear_filter); + goto out_unlock; + } + do_for_each_ftrace_rec(pg, rec) { if (rec->flags & FTRACE_FL_DISABLED) diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index a34fa5e76abb..ae7df090b93e 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -1459,6 +1459,7 @@ enum regex_type { MATCH_MIDDLE_ONLY, MATCH_END_ONLY, MATCH_GLOB, + MATCH_INDEX, }; struct regex { diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c index f052ecb085e9..ade606c33231 100644 --- a/kernel/trace/trace_events_filter.c +++ b/kernel/trace/trace_events_filter.c @@ -825,6 +825,9 @@ enum regex_type filter_parse_regex(char *buff, int len, char **search, int *not) *search = buff; + if (isdigit(buff[0])) + return MATCH_INDEX; + for (i = 0; i < len; i++) { if (buff[i] == '*') { if (!i) { @@ -862,6 +865,8 @@ static void filter_build_regex(struct filter_pred *pred) } switch (type) { + /* MATCH_INDEX should not happen, but if it does, match full */ + case MATCH_INDEX: case MATCH_FULL: r->match = regex_match_full; break; |