linux-kernel - Re: [PATCH 2/2] x86/MCE: Add command line option to extend MCE Records pool

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Date: Fri, 9 Feb 2024 14:02:49 -0600
From: "Naik, Avadhut" <avadnaik@....com>
To: Sohil Mehta <sohil.mehta@...el.com>, x86@...nel.org,
 linux-edac@...r.kernel.org
Cc: bp@...en8.de, tony.luck@...el.com, linux-kernel@...r.kernel.org,
 yazen.ghannam@....com, Avadhut Naik <avadhut.naik@....com>
Subject: Re: [PATCH 2/2] x86/MCE: Add command line option to extend MCE
 Records pool

Hi,

On 2/8/2024 19:36, Sohil Mehta wrote:
> On 2/7/2024 2:56 PM, Avadhut Naik wrote:
>> Extension of MCE Records pool, based on system's CPU count, was undertaken
>> through the previous patch (x86/MCE: Extend size of the MCE Records pool).
>>
> 
> This statement is unnecessary.
>
Noted.
 
>> Add a new command line parameter "mce-genpool-extend" to set the size of
>> MCE Records pool to a predetermined number of pages instead of system's
>> CPU count.
>>
> 
> Like Tony, I am unsure of when this would be useful.
> 
> Also, why does it need to override the CPU count based extension
> mechanism? Would just adding more pages not work for them?
> 
> If there really is a good reason to do this, how about changing
> mce-genpool-extend to mce-genpool-add-pages and keeping the description
> the same?
> 
> mce-genpool-add-pages=	[X86-64] Number of pages to add to MCE Records pool.
> 
> Then you can simply add these many number of additional pages to the new
> CPU based mechanism.
> 
Is it safe to assume that users will always want to increase the size of the
pool and not decrease it?

IMO, the command-line option provides flexibility for users to choose the size of
MCE Records pool in case, they don't agree with the CPU count logic. Just added it
to ensure that we are not enforcing this increased memory footprint across the board.

Would you agree?

-- 
Thanks,
Avadhut Naik

> Sohil
> 
>> Signed-off-by: Avadhut Naik <avadhut.naik@....com>
>> ---
>>  .../admin-guide/kernel-parameters.txt         |  2 ++
>>  arch/x86/kernel/cpu/mce/genpool.c             | 22 ++++++++++++++++---
>>  2 files changed, 21 insertions(+), 3 deletions(-)
>>
>