From: Petr Mladek <pmladek@suse.com>
To: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Prarit Bhargava <prarit@redhat.com>,
John Ogness <john.ogness@linutronix.de>,
Orson Zhai <orson.zhai@unisoc.com>, Baoquan He <bhe@redhat.com>,
cixi.geng1@unisoc.com, Stephen Boyd <sboyd@kernel.org>,
zhang.lyra@gmail.com, Steven Sistare <steven.sistare@oracle.com>,
kexec@lists.infradead.org, linux-kernel@vger.kernel.org,
Steven Rostedt <rostedt@goodmis.org>,
Jon DeVree <nuxi@vault24.org>,
John Stultz <john.stultz@linaro.org>,
ruifeng.zhang1@unisoc.com, Orson Zhai <orsonzhai@gmail.com>,
Thomas Gleixner <tglx@linutronix.de>,
Salvatore Bonaccorso <carnil@debian.org>,
Dave Young <dyoung@redhat.com>,
Dominique Martinet <asmadeus@codewreck.org>,
Vivek Goyal <vgoyal@redhat.com>,
Pavel Tatashin <pasha.tatashin@soleen.com>
Subject: Re: [RFC PATCH] printk: Change timestamp to triplet as mono, boot and real
Date: Fri, 14 Aug 2020 11:50:31 +0200 [thread overview]
Message-ID: <20200814095031.GM6215@alley> (raw)
In-Reply-To: <20200813113155.GA483@jagdpanzerIV.localdomain>
On Thu 2020-08-13 20:31:55, Sergey Senozhatsky wrote:
> On (20/08/13 12:22), Petr Mladek wrote:
> >
> > + would take more space (prefix + text vs. binary representation)
>
> Dict buffer is allocated regardless of how we use it, and only printks
> from drivers/* (dev_printk*) add dict payload. It might be the case
> that on some (if not most) systems dict pages are not used 90% of times
> (if not 99%).
>
> > + not reliable because dict is currently dropped when no space
>
> Well, in the perfect world this is a problem, but "maybe not having
> alternative timestamps sometimes" can be OK approach for people who
> wants to use those triplet timestamps.
I am afraid the people would see missing timestamps as a bug.
They want it because they want to corelate kernel and userspace logs.
The timestamps from realtime clock are supposed to make it
straightforward.
More importantly. I do not see a reasonable way how to handle it.
No timestamp is worse than timestamps from non-synchronized clock.
Mixing timestamps from different clocks (as fallback) would cause
a lot of confusion (more harm than good).
> But, in general, how real this problem is? What I sae so far (on my boxes)
> was that printk messages are longer than dict payload.
Yeah, I think that dict are less used on normal systems. But it might
be very different when a driver gets more verbose during debugging
and the amount of dev_printk() calls is much higher.
Best Regards,
Petr
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WARNING: multiple messages have this Message-ID (diff)
From: Petr Mladek <pmladek@suse.com>
To: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Orson Zhai <orsonzhai@gmail.com>,
Prarit Bhargava <prarit@redhat.com>,
Dave Young <dyoung@redhat.com>, Baoquan He <bhe@redhat.com>,
Vivek Goyal <vgoyal@redhat.com>,
Steven Rostedt <rostedt@goodmis.org>,
John Stultz <john.stultz@linaro.org>,
Stephen Boyd <sboyd@kernel.org>,
kexec@lists.infradead.org, linux-kernel@vger.kernel.org,
zhang.lyra@gmail.com, ruifeng.zhang1@unisoc.com,
cixi.geng1@unisoc.com, Orson Zhai <orson.zhai@unisoc.com>,
Pavel Tatashin <pasha.tatashin@soleen.com>,
Steven Sistare <steven.sistare@oracle.com>,
Dominique Martinet <asmadeus@codewreck.org>,
Jon DeVree <nuxi@vault24.org>,
Salvatore Bonaccorso <carnil@debian.org>,
John Ogness <john.ogness@linutronix.de>
Subject: Re: [RFC PATCH] printk: Change timestamp to triplet as mono, boot and real
Date: Fri, 14 Aug 2020 11:50:31 +0200 [thread overview]
Message-ID: <20200814095031.GM6215@alley> (raw)
In-Reply-To: <20200813113155.GA483@jagdpanzerIV.localdomain>
On Thu 2020-08-13 20:31:55, Sergey Senozhatsky wrote:
> On (20/08/13 12:22), Petr Mladek wrote:
> >
> > + would take more space (prefix + text vs. binary representation)
>
> Dict buffer is allocated regardless of how we use it, and only printks
> from drivers/* (dev_printk*) add dict payload. It might be the case
> that on some (if not most) systems dict pages are not used 90% of times
> (if not 99%).
>
> > + not reliable because dict is currently dropped when no space
>
> Well, in the perfect world this is a problem, but "maybe not having
> alternative timestamps sometimes" can be OK approach for people who
> wants to use those triplet timestamps.
I am afraid the people would see missing timestamps as a bug.
They want it because they want to corelate kernel and userspace logs.
The timestamps from realtime clock are supposed to make it
straightforward.
More importantly. I do not see a reasonable way how to handle it.
No timestamp is worse than timestamps from non-synchronized clock.
Mixing timestamps from different clocks (as fallback) would cause
a lot of confusion (more harm than good).
> But, in general, how real this problem is? What I sae so far (on my boxes)
> was that printk messages are longer than dict payload.
Yeah, I think that dict are less used on normal systems. But it might
be very different when a driver gets more verbose during debugging
and the amount of dev_printk() calls is much higher.
Best Regards,
Petr
next prev parent reply other threads:[~2020-08-14 9:50 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-11 4:40 [RFC PATCH] printk: Change timestamp to triplet as mono, boot and real Orson Zhai
2020-08-11 4:40 ` Orson Zhai
2020-08-11 4:56 ` Randy Dunlap
2020-08-11 4:56 ` Randy Dunlap
2020-08-11 9:44 ` Petr Mladek
2020-08-11 9:44 ` Petr Mladek
2020-08-11 12:05 ` Thomas Gleixner
2020-08-11 12:05 ` Thomas Gleixner
2020-08-11 13:02 ` Petr Mladek
2020-08-11 13:02 ` Petr Mladek
2020-08-11 13:43 ` Prarit Bhargava
2020-08-11 13:43 ` Prarit Bhargava
2020-08-13 1:55 ` Sergey Senozhatsky
2020-08-13 1:55 ` Sergey Senozhatsky
2020-08-13 10:22 ` Petr Mladek
2020-08-13 10:22 ` Petr Mladek
2020-08-13 11:31 ` Sergey Senozhatsky
2020-08-13 11:31 ` Sergey Senozhatsky
2020-08-14 9:50 ` Petr Mladek [this message]
2020-08-14 9:50 ` Petr Mladek
2020-08-13 10:26 ` Thomas Gleixner
2020-08-13 10:26 ` Thomas Gleixner
2020-08-14 6:34 ` Dave Young
2020-08-14 6:34 ` Dave Young
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