Messages in this thread |  | | Date | Wed, 8 Jul 2020 17:20:05 +0200 | From | Petr Mladek <> | Subject | Re: [PATCH v4 0/4] printk: replace ringbuffer |
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On Tue 2020-07-07 17:05:28, John Ogness wrote: > Hello, > > Here is a v4 for the first series to rework the printk > subsystem. The v3 is here [0]. This first series > only replaces the existing ringbuffer implementation. No locking > is removed. The semantics/behavior of printk are kept the same > except for a minor optimization that is reverted (patch 3). > > Despite minor changes to the ringbuffer code since v3 (comments, > function names, very minor refactoring), the ringbuffer logic > itself has not changed. And, in particular, the memory barriers > have been exactly preserved from v3. For this reason I deem it > appropriate to keep Paul's reviewed by tag (patch 2). > > RFC patches for various userspace tools to dump the kernel log > are available: crash [1], makedumpfile [2], kexec-tools [3]. > > Finally, I would like to thank some people/organizations that > helped with performing ringbuffer stress tests on big or rare > hardware that I do not have access to: > > - Prarit Bhargava of Red Hat (x86_64, ppc64le power8) > - Michael Cree of Debian (alpha) > - Jeff Scheel of OSU Open Source Lab (ppc64le power8 kvm)
OK, I think that we are ready to try this in linux-next. I am going to push it there via printk/linux.git.
I have a good feeling about the patchset. The great thing is that the access is still synchronized using logbuf_lock so that we do not have to deal with races for the moment.
Of course, there are still many potential problems. The following comes to my mind:
+ Bugs in the algorithm logic or implementation might prevent showing any messages on consoles or via syslog or /dev/kmsg. We did our best to avoid it.
+ Debugging tools accessing the buffer directly would need to understand the new structure. Fortunately John provided patches for the most prominent ones.
+ Small devices might complain about less effective use of memory. Part of descriptors and dictionaries ring buffers might stay unused. But it hopefully could get tuned.
This is basically just a start of the journey. I hope that it will be a good one.
Best Regards, Petr
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