linux-kernel - Re: [PATCH 0/2] Ajust lockdep static allocations

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Date:   Fri, 23 Sep 2016 15:30:31 -0500
From:   Babu Moger <babu.moger@...cle.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     mingo@...hat.com, akpm@...ux-foundation.org, keescook@...omium.org,
        dan.j.williams@...el.com, aryabinin@...tuozzo.com, tj@...nel.org,
        linux-kernel@...r.kernel.org, Rob Gardner <rob.gardner@...cle.com>,
        davem@...emloft.net
Subject: Re: [PATCH 0/2] Ajust lockdep static allocations


On 9/23/2016 3:17 PM, Peter Zijlstra wrote:
> On Fri, Sep 23, 2016 at 02:57:39PM -0500, Babu Moger wrote:
>
>>   We checked again. Yes, It goes in .bss section. But in sparc we have
>>   to fit .text, .data, .bss in 7 permanent TLBs(that is totally 28MB).
>>   It was fine so far.  But the commit 1413c0389333 ("lockdep: Increase
>>   static allocations") added extra 4MB which makes it go beyond 28MB.
>>   That is causing system boot up problems in sparc.
> *sigh*, why didn't you start with that :/
>
>> Yes.  We know it.  This is a limitation. Changing this limit in our
>> hardware is a much bigger change which we cannot address right away.
>> So, we are trying to come up with a solution which can work for all. I
>> will re-post the patches with  CONFIG_BASE_SMALL option if there is no
>> objections.
> OK, so double check BASE_SMALL doesn't imply other things you cannot
> live with, Sparc64 isn't a dinky system. If BASE_SMALL works for you
> then good, otherwise do a PROVE_LOCKING_SMALL symbol that is not user
> selectable and have SPARC select that. Use the invisible Help for that
> symbol to explain all this again.

      Thanks. Will work on it.

>
>>   CCing David Miller and Rob Gardner. They might be able to explain
>>   more if you have any more questions.
> Nah, I think I remember enough of how the Sparc MMU works to see reason.