On Tue, Apr 15, 2025 at 4:04 AM Louis Chauvet <louis.chauvet@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@gmail.com>
>
> Reviewed-by: Louis Chauvet <louis.chauvet@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
>
>