linux-kernel - Re: [PATCH v10 1/2] printk: Make printk() completely async

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Message-ID: <20160407131532.GA12033@quack2.suse.cz>
Date:	Thu, 7 Apr 2016 15:15:32 +0200
From:	Jan Kara <jack@...e.cz>
To:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Cc:	Jan Kara <jack@...e.cz>, Andrew Morton <akpm@...ux-foundation.org>,
	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
	Jan Kara <jack@...e.com>, Petr Mladek <pmladek@...e.com>,
	Tejun Heo <tj@...nel.org>,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	linux-kernel@...r.kernel.org,
	Byungchul Park <byungchul.park@....com>
Subject: Re: [PATCH v10 1/2] printk: Make printk() completely async

On Thu 07-04-16 21:08:26, Sergey Senozhatsky wrote:
> Hello,
> 
> On (04/07/16 18:48), Sergey Senozhatsky wrote:
> > On (04/06/16 10:27), Jan Kara wrote:
> > [..]
> > > > Well, it's good that we have this.
> > > > 
> > > > It would be better if it was runtime-controllable - changing boot
> > > > parameters is a bit of a pain.  In fact with this approach, your
> > > > zillions-of-scsi-disks scenario becomes less problematic: do the async
> > > > offloading during the boot process then switch back to the more
> > > > reliable sync printing late in boot.
> > > 
> > > Doing this should be relatively easy. It would be userspace's decision
> > > whether they want more reliable or faster printk. Sounds fine with me.
> 
> ok, after some thinking -- it makes a lot of sense to have it. good old
> sync printk is potentially more reliable after all. I think I also now
> want to meke the 'default' for printk_sync being 'true'. so we won't
> spoil printk on the systems that never had any problems with it. at
> least for one release cycle, may be. thus, people would need to request
> async printk via boot param and switch back to sync printk once the booting
> process is done [or keep async printk].
> 
> how does that sound?

That is fine with me. We can always enable this by default in our distro so
that it gets more exposure and big machines are able to boot...

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR