linux-kernel - Re: [PATCH] printk: Add printk_flush() to force buffered text to console

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Message-ID: <20120615043753.GA11155@localhost>
Date:	Fri, 15 Jun 2012 12:37:53 +0800
From:	Fengguang Wu <fengguang.wu@...el.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"kay.sievers" <kay.sievers@...y.org>,
	"Paul E. McKenney" <paulmck@...ibm.com>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] printk: Add printk_flush() to force buffered text to
 console

On Thu, Jun 14, 2012 at 09:30:17PM -0700, Greg Kroah-Hartman 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?

Good question. If the tests are only relevant to the tracing system,
it's better to enable them only when testing the tracing commits. Just
like I won't run ext4 tests for an XFS commit.

Thanks,
Fengguang
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