Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Fri, 14 Feb 2020 10:07:55 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To:     Petr Mladek <pmladek@suse.com>
Cc:     John Ogness <john.ogness@linutronix.de>,
        lijiang <lijiang@redhat.com>,
        Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Andrea Parri <parri.andrea@gmail.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        kexec@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/2] printk: replace ringbuffer
Message-ID: <20200214010755.GA13877@google.com>
References: <20200128161948.8524-1-john.ogness@linutronix.de>
 <dc4ca9b5-d2a2-03af-c186-204a3aad2399@redhat.com>
 <20200205044848.GH41358@google.com>
 <20200205050204.GI41358@google.com>
 <88827ae2-7af5-347b-29fb-cffb94350f8f@redhat.com>
 <20200205063640.GJ41358@google.com>
 <877e11h0ir.fsf@linutronix.de>
 <cd7509a5-48fd-e652-90f4-1e0fe2311134@redhat.com>
 <87sgjp9foj.fsf@linutronix.de>
 <20200213130720.j4e5qv37am2bapup@pathway.suse.cz>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20200213130720.j4e5qv37am2bapup@pathway.suse.cz>
User-Agent: Mutt/1.10.1 (2018-07-13)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On (20/02/13 14:07), Petr Mladek wrote:
> On Wed 2020-02-05 17:12:12, John Ogness wrote:
> > On 2020-02-05, lijiang <lijiang@redhat.com> wrote:
> > > Do you have any suggestions about the size of CONFIG_LOG_* and
> > > CONFIG_PRINTK_* options by default?
> > 
> > The new printk implementation consumes more than double the memory that
> > the current printk implementation requires. This is because dictionaries
> > and meta-data are now stored separately.
> > 
> > If the old defaults (LOG_BUF_SHIFT=17 LOG_CPU_MAX_BUF_SHIFT=12) were
> > chosen because they are maximally acceptable defaults, then the defaults
> > should be reduced by 1 so that the final size is "similar" to the
> > current implementation.
> >
> > If instead the defaults are left as-is, a machine with less than 64 CPUs
> > will reserve 336KiB for printk information (128KiB text, 128KiB
> > dictionary, 80KiB meta-data).
> > 
> > It might also be desirable to reduce the dictionary size (maybe 1/4 the
> > size of text?).
> 
> Good questions. It would be great to check the usage on some real
> systems.

[..]

> I wish the dictionaries were never added ;-) They complicate the code
> and nobody knows how many people actually use the information.

Maybe we can have CONFIG_PRINTK_EXTRA_PAYLOAD [for dicts] so people can
compile it out if it's not needed. This can save several bytes here and
there.

	-ss