hi steve, On 31/03/21 10:09 pm, Steven Rostedt wrote:
On Thu, 1 Apr 2021 22:03:02 +0530 sameeruddin shaik <sameeruddin.shaik8@xxxxxxxxx> wrote:hi steve, On 30/03/21 6:21 am, Steven Rostedt wrote:From: "Steven Rostedt (VMware)" <rostedt@xxxxxxxxxxx> All for full "regex(3)" processing of setting functions in the set_ftrace_filter file. Check if the filter passed in is just a glob expression that the kernel can process, or if it is a regex that should look at the available_filter_functions list instead. If it is a regex, it will read the available_filter_functions and write in each function as it finds it. Link: https://lore.kernel.org/linux-trace-devel/20210323013225.451281989@xxxxxxxxxxx Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx> --- Documentation/libtracefs-function-filter.txt | 10 ++ src/tracefs-tools.c | 139 ++++++++++++++++--- 2 files changed, 128 insertions(+), 21 deletions(-) diff --git a/Documentation/libtracefs-function-filter.txt b/Documentation/libtracefs-function-filter.txt index c0c89f372c21..88aa3b923d54 100644 --- a/Documentation/libtracefs-function-filter.txt +++ b/Documentation/libtracefs-function-filter.txt @@ -32,6 +32,16 @@ _errs_, is a pointer to an array of strings, which will be allocated if any of filters fail to match any available function, If _errs_ is NULL, it will be ignored.+A filter in the array of _filters_ may be either a straight match of a+function, a glob or regex(3). a glob is where '*' matches zero or more +characters, '?' will match zero or one character, and '.' only matches a +period. If the filter is determined to be a regex (where it contains +anything other than alpha numeric characters, or '.', '*', '?') the filter +will be processed as a regex(3) following the rules of regex(3), and '.' is +not a period, but will match any one character. To force a regular +expression, either prefix the filter with a '^' or append it with a '$' as +all filters will act as complete matches of functions anyway. +if we give the filter as regex "^ext4*$" from user side, ideally it should match the ext4 filter functions, if i am not wrong, its not matching any filter in the available_filter_functionsIf you add the "^" and/or "$" it makes it into a regex. The above means that the filter will match "ext", "ext4", "ext44", "ext4444444" Because "*" means zero or more of the previous character. So, unless there's a function that matches one of the above, it wont match anything else. If you left off the "^" and "$" then it would be a glob, where "*" means zero or more of any character. But if you want the same in regex, you need to use: "^ext4.*$"
IF we use the regex in filters, running time of the program is increasing drastically.
lets say,if we give the kernel glob as a filter, its getting converted to regex and running time of program is
5 secs, in other case where we use regex, its taking 80 secs to complete. --sameer.
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