Re: [PATCH v2] kunit: fix failure to build without printk

Joe Perches
2019-08-30T23:36:11Z

On Fri, 2019-08-30 at 23:22 +0000, Tim.Bird@sony.com wrote:
> > -----Original Message-----
> > From: Brendan Higgins
> >
> > On Fri, Aug 30, 2019 at 3:46 PM Joe Perches <joe@perches.com> wrote:
> > > On Fri, 2019-08-30 at 21:58 +0000, Tim.Bird@sony.com wrote:
> > > > > From: Joe Perches
> > > []
> > > > IMHO %pV should be avoided if possible. Just because people are
> > > > doing it doesn't mean it should be used when it is not necessary.
> > >
> > > Well, as the guy that created %pV, I of course
> > > have a different opinion.
> > >
> > > > > then wouldn't it be easier to pass in the
> > > > > > kernel level as a separate parameter and then strip off all printk
> > > > > > headers like this:
> > > > >
> > > > > Depends on whether or not you care for overall
> > > > > object size. Consolidated formats with the
> > > > > embedded KERN_<LEVEL> like suggested are smaller
> > > > > overall object size.
> > > >
> > > > This is an argument I can agree with. I'm generally in favor of
> > > > things that lessen kernel size creep. :-)
> > >
> > > As am I.
> >
> > Sorry, to be clear, we are talking about the object size penalty due
> > to adding a single parameter to a function. Is that right?
>
> Not exactly. The argument is that pre-pending the different KERN_LEVEL
> strings onto format strings can result in several versions of nearly identical strings
> being compiled into the object file. By parameterizing this (that is, adding
> '%s' into the format string, and putting the level into the string as an argument),
> it prevents this duplication of format strings.
>
> I haven't seen the data on duplication of format strings, and how much this
> affects it, but little things can add up. Whether it matters in this case depends
> on whether the format strings that kunit uses are also used elsewhere in the kernel,
> and whether these same format strings are used with multiple kernel message levels.

deduplication can matter as well, but so far
there is little content with kunit_(err|warn|info(=)

kunit/example-test.c: kunit_info(test, "initializing\n");
kunit/test.c: kunit_err(test,
kunit/test.c: kunit_err(test, "%s", fragment->fragment);
kunit/test.c: kunit_err(test, "\n");
kunit/test.c: kunit_err(test, "%s", buf);
kunit/test.c: kunit_err(test, "failed to initialize: %d\n", ret);
kunit/test.c: kunit_err(test, "test case timed out\n");
kunit/test.c: kunit_err(test, "internal error occurred preventing test case from running: %d\n",
kunit/try-catch.c: kunit_err(test, "try timed out\n");
kunit/try-catch.c: kunit_err(test, "wake_up_process() was never called\n");
kunit/try-catch.c: kunit_err(test, "Unknown error: %d\n", exit_code);

Of these, only two do match other kernel uses.

"initializing\n", "failed to initialize: %d\n"