linux-kernel - Re: [v2 PATCH] RISC-V: Optimize tlb flush path.

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Message-ID: <mvma7c4kyo4.fsf@linux-m68k.org>
Date:   Tue, 20 Aug 2019 10:51:07 +0200
From:   Andreas Schwab <schwab@...ux-m68k.org>
To:     Atish Patra <Atish.Patra@....com>
Cc:     "linux-riscv\@lists.infradead.org" <linux-riscv@...ts.infradead.org>,
        "paul.walmsley\@sifive.com" <paul.walmsley@...ive.com>,
        "aou\@eecs.berkeley.edu" <aou@...s.berkeley.edu>,
        "allison\@lohutok.net" <allison@...utok.net>,
        "anup\@brainfault.org" <anup@...infault.org>,
        "linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
        "hch\@infradead.org" <hch@...radead.org>,
        "palmer\@sifive.com" <palmer@...ive.com>
Subject: Re: [v2 PATCH] RISC-V: Optimize tlb flush path.

On Aug 20 2019, Atish Patra <Atish.Patra@....com> wrote:

> +
> +       cpuid = get_cpu();
> +	if (!cmask) {
> +               riscv_cpuid_to_hartid_mask(cpu_online_mask, &hmask);
> +               goto issue_sfence;
> +       }
> +
> +       
> +       if (cpumask_test_cpu(cpuid, cmask) && cpumask_weight(cmask) ==
> 1) {
> +               /* Save trap cost by issuing a local tlb flush here */
> +               if ((start == 0 && size == -1) || (size > PAGE_SIZE))
> +                       local_flush_tlb_all();
> +               else if (size == PAGE_SIZE)
> +                       local_flush_tlb_page(start);
> +               goto done;
> +       }
> +
>         riscv_cpuid_to_hartid_mask(cmask, &hmask);
> +
> +issue_sfence:
>         sbi_remote_sfence_vma(hmask.bits, start, size);
> +done:
> +       put_cpu();
>  }
>
> This is much simpler than what I had done in v2. I will address the if
> condition around size as well.

I still think that this function should be moved out of the header.

Andreas.

-- 
Andreas Schwab, schwab@...ux-m68k.org
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"And now for something completely different."