[PATCH v3 21/54] dyndbg-test: change do_prints testpoint to accept a loopct

[jim.cromie at gmail.com]

On Tue, Apr 15, 2025 at 4:04 AM Louis Chauvet <louis.chauvet at bootlin.com> wrote:
>
>
>
> Le 02/04/2025 à 19:41, Jim Cromie a écrit :
> > echo 1000 > /sys/module/test_dynamic_debug/parameters/do_prints
> >
> > This allows its use as a scriptable load generator, to generate
> > dynamic-prefix-emits for flag combinations vs undecorated messages.
> > This will make it easy to assess the cost of the prefixing.
> >
> > Reading the ./do_prints node also prints messages (once) to the-log.
> >
> > NB: the count is clamped to 10000, chosen to be notice able, but not
> > annoying, and not enough to accidentally flood the logs.
> >
> > Signed-off-by: Jim Cromie <jim.cromie at gmail.com>
>
> Reviewed-by: Louis Chauvet <louis.chauvet at bootlin.com>
>
> I think this could be in a separate series / merged independently to
> reduce the size of this series.

I have no strong opinions here.
I included it to acknowledge that this patchset is mainly for performance,
ie to replace LOTS of bit-tests, (some of which are tested at framerate).
So it follows that I should be able to demonstrate the savings somehow.

I havent done so yet, I was hoping that the benefits are obvious
enough not require proof.




>
> > ---
> >   lib/test_dynamic_debug.c | 37 ++++++++++++++++++++++++++-----------
> >   1 file changed, 26 insertions(+), 11 deletions(-)
> >
> > diff --git a/lib/test_dynamic_debug.c b/lib/test_dynamic_debug.c
> > index 9f9e3fddd7e6..4a3d2612ef60 100644
> > --- a/lib/test_dynamic_debug.c
> > +++ b/lib/test_dynamic_debug.c
> > @@ -29,18 +29,30 @@
> >
> >   #include <linux/module.h>
> >
> > -/* re-gen output by reading or writing sysfs node: do_prints */
> > -
> > -static void do_prints(void); /* device under test */
> > +/* re-trigger debug output by reading or writing sysfs node: do_prints */
> > +#define PRINT_CLAMP 10000
> > +static void do_prints(unsigned int); /* device under test */
> >   static int param_set_do_prints(const char *instr, const struct kernel_param *kp)
> >   {
> > -     do_prints();
> > +     int rc;
> > +     unsigned int ct;
> > +
> > +     rc = kstrtouint(instr, 0, &ct);
> > +     if (rc) {
> > +             pr_err("expecting numeric input, using 1 instead\n");
> > +             ct = 1;
> > +     }
> > +     if (ct > PRINT_CLAMP) {
> > +             ct = PRINT_CLAMP;
> > +             pr_info("clamping print-count to %d\n", ct);
> > +     }
> > +     do_prints(ct);
> >       return 0;
> >   }
> >   static int param_get_do_prints(char *buffer, const struct kernel_param *kp)
> >   {
> > -     do_prints();
> > -     return scnprintf(buffer, PAGE_SIZE, "did do_prints\n");
> > +     do_prints(1);
> > +     return scnprintf(buffer, PAGE_SIZE, "did 1 do_prints\n");
> >   }
> >   static const struct kernel_param_ops param_ops_do_prints = {
> >       .set = param_set_do_prints,
> > @@ -191,17 +203,20 @@ static void do_levels(void)
> >       prdbg(V7);
> >   }
> >
> > -static void do_prints(void)
> > +static void do_prints(unsigned int ct)
> >   {
> > -     pr_debug("do_prints:\n");
> > -     do_cats();
> > -     do_levels();
> > +     /* maybe clamp this */
> > +     pr_debug("do-prints %d times:\n", ct);
> > +     for (; ct; ct--) {
> > +             do_cats();
> > +             do_levels();
> > +     }
> >   }
> >
> >   static int __init test_dynamic_debug_init(void)
> >   {
> >       pr_debug("init start\n");
> > -     do_prints();
> > +     do_prints(1);
> >       pr_debug("init done\n");
> >       return 0;
> >   }
>
> --
> Louis Chauvet, Bootlin
> Embedded Linux and Kernel engineering
> https://bootlin.com
>
>