linux-kernel - Re: [PATCH v2 1/3] x86: Move DEBUG

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Date:   Mon, 29 Apr 2019 14:29:43 -0700
From:   Atish Patra <atish.patra@....com>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Albert Ou <aou@...s.berkeley.edu>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Anup Patel <anup@...infault.org>,
        Borislav Petkov <bp@...en8.de>,
        Changbin Du <changbin.du@...el.com>,
        Gary Guo <gary@...yguo.net>, "H. Peter Anvin" <hpa@...or.com>,
        Ingo Molnar <mingo@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
        Luc Van Oostenryck <luc.vanoostenryck@...il.com>,
        Palmer Dabbelt <palmer@...ive.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vlastimil Babka <vbabka@...e.cz>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        Christoph Hellwig <hch@...radead.org>
Subject: Re: [PATCH v2 1/3] x86: Move DEBUG_TLBFLUSH option.

On 4/29/19 1:06 PM, Ingo Molnar wrote:
> 
> * Atish Patra <atish.patra@....com> wrote:
> 
>> CONFIG_DEBUG_TLBFLUSH was added in 'commit 3df3212f9722 ("x86/tlb: add
>> tlb_flushall_shift knob into debugfs")' to support tlb_flushall_shift
>> knob. The knob was removed in 'commit e9f4e0a9fe27 ("x86/mm: Rip out
>> complicated, out-of-date, buggy TLB flushing")'.  However, the debug
>> option was never removed from Kconfig. It was reused in commit
>> '9824cf9753ec ("mm: vmstats: tlb flush counters")' but the commit text
>> was never updated accordingly.
> 
> Please, when you mention several commits, put them into new lines to make
> it readable, i.e.:
> 
>    3df3212f9722 ("x86/tlb: add tlb_flushall_shift knob into debugfs")
> 
> etc.
> 
Done.

>> Update the Kconfig option description as per its current usage.
>>
>> Take this opprtunity to make this kconfig option a common option as it
>> touches the common vmstat code. Introduce another arch specific config
>> HAVE_ARCH_DEBUG_TLBFLUSH that can be selected to enable this config.
> 
> "opprtunity"?
> 
>> +config HAVE_ARCH_DEBUG_TLBFLUSH
>> +	bool
>> +	depends on DEBUG_KERNEL
>> +
>> +config DEBUG_TLBFLUSH
>> +	bool "Save tlb flush statstics to vmstat"
>> +	depends on HAVE_ARCH_DEBUG_TLBFLUSH
>> +	help
>> +
>> +	Add tlbflush statstics to vmstat. It is really helpful understand tlbflush
>> +	performance and behavior. It should be enabled only for debugging purpose
>> +	by individual architectures explicitly by selecting HAVE_ARCH_DEBUG_TLBFLUSH.
> 
> "statstics"??
> 
> Please put a spell checker into your workflow or read what you are
> writing ...
> 

Apologies for the typos. Fixed them.

Regards,
Atish
> Thanks,
> 
> 	Ingo
>