`On Tue, Oct 19, 2021 at 7:28 PM Steven Rostedt <rostedt@goodmis.org> wrote:>> On Tue, 19 Oct 2021 18:31:39 -0700> Kalesh Singh <kaleshsingh@google.com> wrote:>> > +static u64 hist_field_div(struct hist_field *hist_field,> > +                        struct tracing_map_elt *elt,> > +                        struct trace_buffer *buffer,> > +                        struct ring_buffer_event *rbe,> > +                        void *event)> > +{> > +     struct hist_field *operand1 = hist_field->operands[0];> > +     struct hist_field *operand2 = hist_field->operands[1];> > +> > +     u64 val1 = operand1->fn(operand1, elt, buffer, rbe, event);> > +     u64 val2 = operand2->fn(operand2, elt, buffer, rbe, event);> > +> > +     /* Return -1 for the undefined case */> > +     if (!val2)> > +             return -1;> > +> > +     return div64_u64(val1, val2);> > +}> > +>> I wonder if you should add a shift operator as well?>> I mean, if for some reason you want to divide by a power of two, then why> us the division. Especially if this is on a 32 bit machine.>> Of course, the parsing could detect that. If the divisor is a constant. Or> we could even optimize the above with:>>         if (!val2)>                 return -1;>>         if (!(val2 & (val2 - 1))>                 return val1 >> __ffs64(val2);>> Which should be faster than a divide, and even if it isn't a power of two,> the subtract and & should be in the noise compared to the divide.>> Note, the above can be added to this. I'm not suggesting changing this> patch.Is it worth adding something like this for the multiplication case as well?- Kalesh>> -- Steve`