From: Brendan Higgins <brendanhiggins@google.com>
To: Tim.Bird@sony.com
Cc: joe@perches.com, shuah@kernel.org,
sergey.senozhatsky.work@gmail.com, kunit-dev@googlegroups.com,
linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
frowand.list@gmail.com, sboyd@kernel.org, pmladek@suse.com,
sergey.senozhatsky@gmail.com, rostedt@goodmis.org,
rdunlap@infradead.org, sfr@canb.auug.org.au
Subject: Re: [PATCH v2] kunit: fix failure to build without printk
Date: Fri, 30 Aug 2019 16:37:10 -0700 [thread overview]
Message-ID: <20190830233710.GA101591@google.com> (raw)
In-Reply-To: <ECADFF3FD767C149AD96A924E7EA6EAF977A8416@USCULXMSG01.am.sony.com>
On Fri, Aug 30, 2019 at 11:22:43PM +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.
> -- Tim
I thought this portion of the discussion was about whether Joe's version
of kunit_printk was better or my critique of his version of kunit_printk:
Joe's:
> > > > -void kunit_printk(const char *level,
> > > > - const struct kunit *test,
> > > > - const char *fmt, ...)
> > > > +void kunit_printk(const struct kunit *test, const char *fmt, ...)
> > > > {
> > > > + char lvl[PRINTK_MAX_SINGLE_HEADER_LEN + 1] = "\0";
> > > > struct va_format vaf;
> > > > va_list args;
> > > > + int kern_level;
> > > >
> > > > va_start(args, fmt);
> > > >
> > > > + while ((kern_level = printk_get_level(fmt)) != 0) {
> > > > + size_t size = printk_skip_level(fmt) - fmt;
> > > > +
> > > > + if (kern_level >= '0' && kern_level <= '7') {
> > > > + memcpy(lvl, fmt, size);
> > > > + lvl[size] = '\0';
> > > > + }
> > > > + fmt += size;
> > > > + }
> > > > +
> > > > vaf.fmt = fmt;
> > > > vaf.va = &args;
> > > >
> > > > - kunit_vprintk(test, level, &vaf);
> > > > + printk("%s\t# %s %pV\n", lvl, test->name, &vaf);
> > > >
> > > > va_end(args);
> > > > }
Mine:
> void kunit_printk(const char *level,
> const struct kunit *test,
> const char *fmt, ...)
> {
> struct va_format vaf;
> va_list args;
>
> va_start(args, fmt);
>
> + fmt = printk_skip_headers(fmt);
> +
> vaf.fmt = fmt;
> vaf.va = &args;
>
> - kunit_vprintk(test, level, &vaf);
> + printk("%s\t# %s %pV\n", level, test->name, &vaf);
>
> va_end(args);
> }
I thought you and Joe were arguing that "Joe's" resulted in a smaller
object size than "Mine" (not to be confused with the actual patch I
presented here, which is what Sergey suggested I do on a different
thread).
I really don't feel strongly about what Sergey suggested I do (which is
what this patch originally introduced), versus, what Joe suggested,
versus what I suggested in response to Joe (or any of the things
suggested on other threads). I just want to pick one, fix the breakage
in linux-next, and move on with my life.
Cheers
next prev parent reply other threads:[~2019-08-30 23:37 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-28 9:31 [PATCH v2] kunit: fix failure to build without printk Brendan Higgins
2019-08-28 9:49 ` Sergey Senozhatsky
2019-08-28 11:50 ` Petr Mladek
2019-08-29 17:01 ` shuah
2019-08-30 4:44 ` Joe Perches
2019-08-30 4:56 ` Joe Perches
2019-08-30 18:38 ` Brendan Higgins
2019-08-30 20:46 ` Joe Perches
2019-08-30 21:58 ` Tim.Bird
2019-08-30 22:46 ` Joe Perches
2019-08-30 23:02 ` Brendan Higgins
2019-08-30 23:22 ` Tim.Bird
2019-08-30 23:36 ` Joe Perches
2019-08-30 23:37 ` Brendan Higgins [this message]
2019-08-30 23:43 ` Joe Perches
2019-08-31 0:06 ` Tim.Bird
2019-09-02 12:52 ` Petr Mladek
2019-09-02 14:39 ` shuah
2019-08-30 23:29 ` Tim.Bird
2019-08-30 5:19 ` Sergey Senozhatsky
2019-08-28 15:52 ` Randy Dunlap
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190830233710.GA101591@google.com \
--to=brendanhiggins@google.com \
--cc=Tim.Bird@sony.com \
--cc=frowand.list@gmail.com \
--cc=joe@perches.com \
--cc=kunit-dev@googlegroups.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-kselftest@vger.kernel.org \
--cc=pmladek@suse.com \
--cc=rdunlap@infradead.org \
--cc=rostedt@goodmis.org \
--cc=sboyd@kernel.org \
--cc=sergey.senozhatsky.work@gmail.com \
--cc=sergey.senozhatsky@gmail.com \
--cc=sfr@canb.auug.org.au \
--cc=shuah@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).