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SubjectRe: [PATCH 1/4] printk: Allocate kernel log buffer earlier


Ingo Molnar wrote:
> * Mike Travis <travis@sgi.com> wrote:
>
>> On larger systems, because of the numerous ACPI, Bootmem and EFI
>> messages, the static log buffer overflows before the larger one
>> specified by the log_buf_len param is allocated. Minimize the
>> potential for overflow by allocating the new log buffer as soon
>> as possible.
>>
>> We do this by changing the log_buf_len from an early_param to a
>> _setup param. But _setup params are processed before the
>> alloc_bootmem is available, so this function will now just save
>> the requested log buf len. The real work routine (setup_log_buf)
>> is called after bootmem is available.
>>
>> Signed-off-by: Mike Travis <travis@sgi.com>
>> Reviewed-by: Jack Steiner <steiner@sgi.com>
>> Reviewed-by: Robin Holt <holt@sgi.com>
>> ---
>> arch/x86/kernel/setup.c | 5 +++
>> include/linux/printk.h | 4 ++
>> init/main.c | 1
>> kernel/printk.c | 75 ++++++++++++++++++++++++++++--------------------
>> 4 files changed, 54 insertions(+), 31 deletions(-)
>
> Well, the modern allocation method is memblock - available on all major
> architectures.
>
> You could avoid all this ugly workaround of bootmem limitations by moving the
> allocation to memblock_alloc() and desupporting the log_buf_len= boot parameter
> on non-memblock architectures.

Is it really that ugly? I thought in some ways it cleaned it up.

I'm also hesitant to change code for other arch's when I can't test them. This
approach seemed to be the safest.

> kernel log buffer size can be configured via the .config so they will not be left
> without larger buffers.

We have asked about this, but distros are reluctant to increase memory usage
for their entire installed base. I think we're lucky they bumped it up to 256k
from the default 128k.

>
> Doing this should also have the advantage of getting all the early x86 messages into
> the larger buffer already, reducing the pressure to apply some of the other patches
> in your series.

There are only two and both remove only redundant information.

>
> Thanks,
>
> Ingo


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