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Date: Fri, 15 Jun 2012 16:13:18 -0700
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Ingo Molnar <mingo@kernel.org>
Cc: Fengguang Wu <fengguang.wu@intel.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        "kay.sievers" <kay.sievers@vrfy.org>,
        "Paul E. McKenney" <paulmck@us.ibm.com>, Ingo Molnar <mingo@elte.hu>,
        Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] printk: Add printk_flush() to force buffered text to
 console
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On Fri, Jun 15, 2012 at 02:04:30PM +0200, Ingo Molnar wrote:
> 
> * Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote:
> 
> > On Fri, Jun 15, 2012 at 12:22:33PM +0800, Fengguang Wu wrote:
> > > > I actually would like to make these more compact. As all my test box
> > > > consoles go through serial ports, just booting through this takes more
> > > > time the the compile itself.
> > > 
> > > The tests took 23 seconds boot time on one kernel:
> > > 
> > >         [    0.152934] Testing tracer nop: PASSED
> > >         ...1577 lines total...
> > >         [   23.206550] Testing kprobe tracing: OK
> > > 
> > > And 135 seconds in another bloated kernel:
> > > 
> > >         [  115.396441] Testing event 9p_client_req: OK
> > >         ...2545 lines total...
> > >         [  240.268783] Testing kprobe tracing: OK
> > > 
> > > I'd appreciate if the boot time can be reduced. Because I'm doing
> > > kernel boot tests for *every single* commits.
> > > 
> > > It may look insane amount of work, but it's still manageable: with 10
> > > kvm instances each take 1 minute to boot test a kernel, I can boot
> > > test 60*24*10=14400 kernels in one day. That's a rather big number.
> > > That allows me to run more cpu/vm/io stress tests for each kernel :-)
> > 
> > Do you really want to enable those tests for your test 
> > kernels?  Can they fail if we mess up other parts of the 
> > kernel, or do they only test the tracing portions?
> 
> These printk's are useful, are used for a specific (albeit 
> limited) purpose and were and continue to be useful in that 
> role.
> 
> The changes Steve bisected to broke this use of printk().

And note, fixed others :)

> Please apply Steve's fix, fix it yourself or revert the changes that
> regressed printk().

I thought Steve's patch was just a RFC thing, is it really something
that everyone wants to see applied?

thanks,

greg k-h