Messages in this thread | | | From | John Ogness <> | Subject | Re: [PATCH 0/2] printk: replace ringbuffer | Date | Wed, 05 Feb 2020 17:12:12 +0100 |
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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?). However, since the new printk implementation allows for non-intrusive dictionaries, we might see their usage increase and start to be as large as the messages themselves.
John Ogness
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