Re: [Xen-devel] [PATCH for-xen-4.5] console: increase initial conring size

["Jan Beulich" <jbeulich@xxxxxxxx>]

>>> Daniel Kiper <daniel.kiper@xxxxxxxxxx> 12/02/14 3:58 PM >>>
>In general initial conring size is sufficient. However, if log
>level is increased on platforms which have e.g. huge number
>of memory regions (I have an IBM System x3550 M2 with 8 GiB RAM
>which has more than 200 entries in EFI memory map) then some
>of earlier messages in console ring are overwritten. It means
>that in case of issues deeper analysis can be hindered. Sadly
>conring_size argument does not help because new console buffer
>is allocated late on heap. It means that it is not possible to
>allocate larger ring earlier. So, in this situation initial
>conring size should be increased. My experiments showed that
>even on not so big machines more than 26 KiB of free space are
>needed for initial messages. In theory we could increase conring
>size buffer to 32 KiB. However, I think that this value could be
>too small for huge machines with large number of ACPI tables and
>EFI memory regions. Hence, this patch increases initial conring
>size to 64 KiB.
>
>Signed-off-by: Daniel Kiper <daniel.kiper@xxxxxxxxxx>

I think it was made clear before that just saying "for-xen-4.5" without any
further rationale is insufficient. Please explain what makes this so important
a change that it needs to go in now.

Apart from that, as Olaf validly replied, setting up a dynamically allocated
buffer earlier would seem like a much better course of action.

Jan


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