From f79b3f338564e7674dbe6375bcf685c2ba483efe Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (VMware)" Date: Mon, 11 Feb 2019 15:00:48 -0500 Subject: ftrace: Allow enabling of filters via index of available_filter_functions Enabling of large number of functions by echoing in a large subset of the functions in available_filter_functions can take a very long time. The process requires testing all functions registered by the function tracer (which is in the 10s of thousands), and doing a kallsyms lookup to convert the ip address into a name, then comparing that name with the string passed in. When a function causes the function tracer to crash the system, a binary bisect of the available_filter_functions can be done to find the culprit. But this requires passing in half of the functions in available_filter_functions over and over again, which makes it basically a O(n^2) operation. With 40,000 functions, that ends up bing 1,600,000,000 opertions! And enabling this can take over 20 minutes. As a quick speed up, if a number is passed into one of the filter files, instead of doing a search, it just enables the function at the corresponding line of the available_filter_functions file. That is: # echo 50 > set_ftrace_filter # cat set_ftrace_filter x86_pmu_commit_txn # head -50 available_filter_functions | tail -1 x86_pmu_commit_txn This allows setting of half the available_filter_functions to take place in less than a second! # time seq 20000 > set_ftrace_filter real 0m0.042s user 0m0.005s sys 0m0.015s # wc -l set_ftrace_filter 20000 set_ftrace_filter Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/trace.h | 1 + 1 file changed, 1 insertion(+) (limited to 'kernel/trace/trace.h') 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 { -- cgit v1.2.3