From: Arnd Bergmann <arnd@arndb.de>
To: "Chris Friesen" <cfriesen@nortel.com>
Cc: Maxim Levitsky <maximlevitsky@gmail.com>,
Frederic Weisbecker <fweisbec@gmail.com>,
linuxppc-dev@lists.ozlabs.org,
linux-kernel <linux-kernel@vger.kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Dave Jones <davej@redhat.com>, Ingo Molnar <mingo@elte.hu>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
Arjan van de Ven <arjan@infradead.org>
Subject: Re: RFC: Put printk buffer in video ram
Date: Mon, 23 Nov 2009 20:03:31 +0100 [thread overview]
Message-ID: <200911232003.31482.arnd@arndb.de> (raw)
In-Reply-To: <4B0ADA84.5050300@nortel.com>
On Monday 23 November 2009, Chris Friesen wrote:
> We've had a mechanism sort of like this for quite a while. Hasn't been
> pushed to mainline because it used board-specific hardware and we're
> usually multiple kernel versions behind mainline.
>
> Anyways, a couple things that we've found to be useful are:
> 1) The ability to allocate a chunk of this persistent memory area for a
> special purpose. This allows things like memory-mapped circular buffers
> for per-cpu binary data.
> 2) An API to log just to this persistent area and bypass the normal
> console completely. This can be useful when debugging issues where the
> normal logging paths result in a hang.
Some powerpc machines have a memory-mapped nvram, in which the kernel
can install persistant 'partitions'. Not all of them are memory mapped,
but for those that are (e.g. IBM QS22), your approach sounds perfect.
Arnd <><
WARNING: multiple messages have this Message-ID (diff)
From: Arnd Bergmann <arnd@arndb.de>
To: "Chris Friesen" <cfriesen@nortel.com>
Cc: Ingo Molnar <mingo@elte.hu>,
Maxim Levitsky <maximlevitsky@gmail.com>,
Frederic Weisbecker <fweisbec@gmail.com>,
Arjan van de Ven <arjan@infradead.org>,
Dave Jones <davej@redhat.com>,
"linux-kernel" <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Steven Rostedt <rostedt@goodmis.org>,
Andrew Morton <akpm@linux-foundation.org>,
linuxppc-dev@lists.ozlabs.org
Subject: Re: RFC: Put printk buffer in video ram
Date: Mon, 23 Nov 2009 20:03:31 +0100 [thread overview]
Message-ID: <200911232003.31482.arnd@arndb.de> (raw)
In-Reply-To: <4B0ADA84.5050300@nortel.com>
On Monday 23 November 2009, Chris Friesen wrote:
> We've had a mechanism sort of like this for quite a while. Hasn't been
> pushed to mainline because it used board-specific hardware and we're
> usually multiple kernel versions behind mainline.
>
> Anyways, a couple things that we've found to be useful are:
> 1) The ability to allocate a chunk of this persistent memory area for a
> special purpose. This allows things like memory-mapped circular buffers
> for per-cpu binary data.
> 2) An API to log just to this persistent area and bypass the normal
> console completely. This can be useful when debugging issues where the
> normal logging paths result in a hang.
Some powerpc machines have a memory-mapped nvram, in which the kernel
can install persistant 'partitions'. Not all of them are memory mapped,
but for those that are (e.g. IBM QS22), your approach sounds perfect.
Arnd <><
next prev parent reply other threads:[~2009-11-23 19:04 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-11-22 2:05 RFC: Put printk buffer in video ram Maxim Levitsky
2009-11-22 2:32 ` Frederic Weisbecker
2009-11-22 8:25 ` Ingo Molnar
2009-11-22 12:15 ` Maxim Levitsky
2009-11-23 1:01 ` Maxim Levitsky
2009-11-23 18:32 ` Ingo Molnar
2009-11-23 18:55 ` Chris Friesen
2009-11-23 19:03 ` Arnd Bergmann [this message]
2009-11-23 19:03 ` Arnd Bergmann
2009-11-22 12:07 ` Maxim Levitsky
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