On Tue, Oct 19, 2021 at 1:48 PM Steven Rostedt <rostedt@xxxxxxxxxxx> wrote: > > On Wed, 15 Sep 2021 19:52:45 +0000 > Kalesh Singh <kaleshsingh@xxxxxxxxxx> wrote: > > > Currently hist trigger expressions don't support the use of numeric > > literals: > > e.g. echo 'hist:keys=common_pid:x=$y-1234' > > --> is not valid expression syntax > > > > Having the ability to use numeric constants in hist triggers supports > > a wider range of expressions for creating variables. > > I'm not against the patch, but I'm curious to what use case this would be > useful for. In the cover letter it mentions the division and multiplication > for finding associated buckets, but what is the addition / subtraction used > for? Addition and subtraction are already supported operations. The use case given in Documentation/trace/histogram.rst is for calculating latencies. I don't have a use case where the constants may be needed in the addition/subtraction, but for simplicity and completeness we support them for all operations. - Kalesh > > -- Steve > > > > > > Add support for creating trace event histogram variables from numeric > > literals. > > > > e.g. echo 'hist:keys=common_pid:x=1234,y=size-1024' >> event/trigger > > > > A negative numeric constant is created, using unary minus operator > > (parentheses are required). > > > > e.g. echo 'hist:keys=common_pid:z=-(2)' >> event/trigger > > > > Signed-off-by: Kalesh Singh <kaleshsingh@xxxxxxxxxx> > >
