linux-kernel - Re: [PATCH 05/17] asm-generic/tlb: Rename HAVE_RCU_TABLE_NO

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Date:   Mon, 16 Dec 2019 18:43:53 +0530
From:   "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Will Deacon <will@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Nick Piggin <npiggin@...il.com>, linux-arch@...r.kernel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>,
        "David S. Miller" <davem@...emloft.net>,
        Helge Deller <deller@....de>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Paul Burton <paulburton@...nel.org>,
        Tony Luck <tony.luck@...el.com>,
        Richard Henderson <rth@...ddle.net>,
        Nick Hu <nickhu@...estech.com>,
        Paul Walmsley <paul.walmsley@...ive.com>
Subject: Re: [PATCH 05/17] asm-generic/tlb: Rename
 HAVE_RCU_TABLE_NO_INVALIDATE

On 12/16/19 6:07 PM, Peter Zijlstra wrote:
> On Mon, Dec 16, 2019 at 06:01:58PM +0530, Aneesh Kumar K.V wrote:
>> Peter Zijlstra <peterz@...radead.org> writes:
>>
>>> Towards a more consistent naming scheme.
>>>
>>> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
>>> ---
>>>   arch/Kconfig              |    3 ++-
>>>   arch/powerpc/Kconfig      |    2 +-
>>>   arch/sparc/Kconfig        |    2 +-
>>>   include/asm-generic/tlb.h |    2 +-
>>>   mm/mmu_gather.c           |    2 +-
>>>   5 files changed, 6 insertions(+), 5 deletions(-)
>>>
>>> --- a/arch/Kconfig
>>> +++ b/arch/Kconfig
>>> @@ -396,8 +396,9 @@ config HAVE_ARCH_JUMP_LABEL_RELATIVE
>>>   config MMU_GATHER_RCU_TABLE_FREE
>>>   	bool
>>>   
>>> -config HAVE_RCU_TABLE_NO_INVALIDATE
>>> +config MMU_GATHER_NO_TABLE_INVALIDATE
>>>   	bool
>>> +	depends on MMU_GATHER_RCU_TABLE_FREE
>>
>>
>> Can we drop this Kernel config option instead use
>> MMU_GATHER_RCU_TABLE_FREE? IMHO reducing the kernel config related to
>> mmu_gather can reduce the complexity.
> 
> I'm confused, are you saing you're happy to have PowerPC eat the extra
> TLB invalidates? I thought you cared about PPC performance :-)
> 
> 

Instead can we do

static inline void tlb_table_invalidate(struct mmu_gather *tlb)
{
#ifndef CONFIG_MMU_GATHER_RCU_TABLE_FREE
	 * Invalidate page-table caches used by hardware walkers. Then we still
	 * need to RCU-sched wait while freeing the pages because software
	 * walkers can still be in-flight.
	 */
	tlb_flush_mmu_tlbonly(tlb);
#endif
}

-aneesh