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Message-ID: <ffdf1eb1-c188-b161-0e70-cad6f64c6c46@linux.alibaba.com>
Date:   Tue, 15 Nov 2022 14:44:44 +0800
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Subject: Re: [PATCH v6 1/2] mm/tlbbatch: Introduce
 arch_tlbbatch_should_defer()
To:     Yicong Yang <yangyicong@huawei.com>, akpm@linux-foundation.org,
        linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org,
        x86@kernel.org, catalin.marinas@arm.com, will@kernel.org,
        anshuman.khandual@arm.com, linux-doc@vger.kernel.org
Cc:     corbet@lwn.net, peterz@infradead.org, arnd@arndb.de,
        punit.agrawal@bytedance.com, linux-kernel@vger.kernel.org,
        darren@os.amperecomputing.com, yangyicong@hisilicon.com,
        huzhanyuan@oppo.com, lipeifeng@oppo.com, zhangshiming@oppo.com,
        guojian@oppo.com, realmz6@gmail.com, linux-mips@vger.kernel.org,
        openrisc@lists.librecores.org, linuxppc-dev@lists.ozlabs.org,
        linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org,
        Barry Song <21cnbao@gmail.com>, wangkefeng.wang@huawei.com,
        prime.zeng@hisilicon.com,
        Anshuman Khandual <khandual@linux.vnet.ibm.com>,
        Barry Song <baohua@kernel.org>
References: <20221115031425.44640-1-yangyicong@huawei.com>
 <20221115031425.44640-2-yangyicong@huawei.com>
From:   haoxin <xhao@linux.alibaba.com>
In-Reply-To: <20221115031425.44640-2-yangyicong@huawei.com>
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在 2022/11/15 上午11:14, Yicong Yang 写道:
> From: Anshuman Khandual <khandual@linux.vnet.ibm.com>
>
> The entire scheme of deferred TLB flush in reclaim path rests on the
> fact that the cost to refill TLB entries is less than flushing out
> individual entries by sending IPI to remote CPUs. But architecture
> can have different ways to evaluate that. Hence apart from checking
> TTU_BATCH_FLUSH in the TTU flags, rest of the decision should be
> architecture specific.
>
> Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>
> [https://lore.kernel.org/linuxppc-dev/20171101101735.2318-2-khandual@linux.vnet.ibm.com/]
> Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
> [Rebase and fix incorrect return value type]
> Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
> Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
> Reviewed-by: Barry Song <baohua@kernel.org>
> Tested-by: Punit Agrawal <punit.agrawal@bytedance.com>
> ---
>   arch/x86/include/asm/tlbflush.h | 12 ++++++++++++
>   mm/rmap.c                       |  9 +--------
>   2 files changed, 13 insertions(+), 8 deletions(-)
>
> diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
> index cda3118f3b27..8a497d902c16 100644
> --- a/arch/x86/include/asm/tlbflush.h
> +++ b/arch/x86/include/asm/tlbflush.h
> @@ -240,6 +240,18 @@ static inline void flush_tlb_page(struct vm_area_struct *vma, unsigned long a)
>   	flush_tlb_mm_range(vma->vm_mm, a, a + PAGE_SIZE, PAGE_SHIFT, false);
>   }
>   
> +static inline bool arch_tlbbatch_should_defer(struct mm_struct *mm)
> +{
> +	bool should_defer = false;
> +
> +	/* If remote CPUs need to be flushed then defer batch the flush */
> +	if (cpumask_any_but(mm_cpumask(mm), get_cpu()) < nr_cpu_ids)
> +		should_defer = true;
> +	put_cpu();
> +
> +	return should_defer;
> +}
> +
>   static inline u64 inc_mm_tlb_gen(struct mm_struct *mm)
>   {
>   	/*
> diff --git a/mm/rmap.c b/mm/rmap.c
> index 2ec925e5fa6a..a9ab10bc0144 100644
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -685,17 +685,10 @@ static void set_tlb_ubc_flush_pending(struct mm_struct *mm, bool writable)
>    */
>   static bool should_defer_flush(struct mm_struct *mm, enum ttu_flags flags)
>   {
> -	bool should_defer = false;
> -
>   	if (!(flags & TTU_BATCH_FLUSH))
>   		return false;
>   
> -	/* If remote CPUs need to be flushed then defer batch the flush */
> -	if (cpumask_any_but(mm_cpumask(mm), get_cpu()) < nr_cpu_ids)
> -		should_defer = true;
> -	put_cpu();
> -
> -	return should_defer;
> +	return arch_tlbbatch_should_defer(mm);
>   }
>   
LGTM, thanks

Reviewed-by: Xin Hao <xhao@linux.alibaba.com>
>   /*