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From:   David Laight <David.Laight@ACULAB.COM>
To:     'Steven Rostedt' <rostedt@goodmis.org>,
        Rasmus Villemoes <rasmus.villemoes@prevas.dk>
CC:     Petr Mladek <pmladek@suse.com>,
        John Ogness <john.ogness@linutronix.de>,
        Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH printk 3/5] printk: use buffer pool for sprint buffers
Thread-Topic: [PATCH printk 3/5] printk: use buffer pool for sprint buffers
Thread-Index: AQHWly6i3uftD0MwYEu+n/WNbQR9JamBPhZA
Date:   Wed, 30 Sep 2020 14:32:12 +0000
Message-ID: <3d6c42b0734a4713b45647415a51bcc1@AcuMS.aculab.com>
References: <20200922153816.5883-1-john.ogness@linutronix.de>
        <20200922153816.5883-4-john.ogness@linutronix.de>
        <20200923151129.GC6442@alley>
        <aef3626f-56a0-9040-fc0e-224ada032d02@prevas.dk>
        <2c95c16b-03e7-eadd-d3af-bedc6b0b471e@prevas.dk>
        <20200925082822.GL29288@alley>
        <4e36f308-a435-f9c1-2d4f-362e797c764e@prevas.dk>
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From: Steven Rostedt
> Sent: 30 September 2020 14:36
> 
> On Wed, 30 Sep 2020 10:06:24 +0200
> Rasmus Villemoes <rasmus.villemoes@prevas.dk> wrote:
> 
> > True. But remember that printk is called from _everywhere_, with all
> > sorts of locks held and/or preemption disabled or whatnot, and every
> > cycle spent in printk makes those windows wider. Doubling the cost of
> > every single printk by unconditionally doing vsnprintf() twice is a bad
> > idea.
> 
> But the console output is usually magnitudes more expensive than the
> vsnprintf(), would doing it twice really make a difference?

Are there any strange %pX modifiers that do anything really horrid?

	David

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