----- On Mar 17, 2022, at 12:07 PM, rostedt rostedt@xxxxxxxxxxx wrote:
> On Thu, 17 Mar 2022 09:32:55 -0400 (EDT)
> Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx> wrote:
>
>> Unless there is a particular reason for using preprocessor defines here, the
>> following form is typically better because it does not pollute the preprocessor
>> defines, e.g.:
>>
>> enum lock_contention_flags {
>> LCB_F_SPIN = 1U << 0;
>> LCB_F_READ = 1U << 1;
>> LCB_F_WRITE = 1U << 2;
>> LCB_F_RT = 1U << 3;
>> LCB_F_PERCPU = 1U << 4;
>> };
>
> If you do this, then to use the __print_flags(), You'll also need to add:
>
> TRACE_DEFINE_ENUM(LCB_F_SPIN);
> TRACE_DEFINE_ENUM(LCB_F_READ);
> TRACE_DEFINE_ENUM(LCB_F_WRITE);
> TRACE_DEFINE_ENUM(LCB_F_RT);
> TRACE_DEFINE_ENUM(LCB_F_PERCPU);
>
> Which does slow down boot up slightly.
So it looks like there is (currently) a good reason for going with the #define.
As a side-discussion, I keep finding it odd that this adds overhead on boot. I suspect
this is also implemented as a linked list which needs to be iterated over at boot-time.
With a few changes to these macros, these linked lists could be turned into arrays,
and thus remove the boot-time overhead.
Thanks,
Mathieu
>
> -- Steve
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
