[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <ZZV19owFbjOzgG89@xhacker>
Date: Wed, 3 Jan 2024 22:57:58 +0800
From: Jisheng Zhang <jszhang@...nel.org>
To: Samuel Holland <samuel.holland@...ive.com>
Cc: Palmer Dabbelt <palmer@...belt.com>, linux-riscv@...ts.infradead.org,
linux-kernel@...r.kernel.org, linux-mm@...ck.org,
Alexandre Ghiti <alexghiti@...osinc.com>
Subject: Re: [PATCH v4 04/12] riscv: Only send remote fences when some other
CPU is online
On Tue, Jan 02, 2024 at 02:00:41PM -0800, Samuel Holland wrote:
> If no other CPU is online, a local cache or TLB flush is sufficient.
> These checks can be constant-folded when SMP is disabled.
>
> Signed-off-by: Samuel Holland <samuel.holland@...ive.com>
> ---
>
> Changes in v4:
> - New patch for v4
>
> arch/riscv/mm/cacheflush.c | 4 +++-
> arch/riscv/mm/tlbflush.c | 4 +++-
> 2 files changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/arch/riscv/mm/cacheflush.c b/arch/riscv/mm/cacheflush.c
> index 47c485bc7df0..f7933ae88a55 100644
> --- a/arch/riscv/mm/cacheflush.c
> +++ b/arch/riscv/mm/cacheflush.c
> @@ -21,7 +21,9 @@ void flush_icache_all(void)
> {
> local_flush_icache_all();
>
> - if (riscv_use_sbi_for_rfence())
> + if (num_online_cpus() < 2)
with patch5, I think it's better to short cut for !SMP, I.E
if (!IS_ENABLED(CONFIG_SMP) || num_online_cpus()) < 2)
so that the UP case can avoid a atomic read and check
> + return;
> + else if (riscv_use_sbi_for_rfence())
> sbi_remote_fence_i(NULL);
> else
> on_each_cpu(ipi_remote_fence_i, NULL, 1);
> diff --git a/arch/riscv/mm/tlbflush.c b/arch/riscv/mm/tlbflush.c
> index 2f18fe6fc4f3..37b3c93e3c30 100644
> --- a/arch/riscv/mm/tlbflush.c
> +++ b/arch/riscv/mm/tlbflush.c
> @@ -73,7 +73,9 @@ static void __ipi_flush_tlb_all(void *info)
>
> void flush_tlb_all(void)
> {
> - if (riscv_use_sbi_for_rfence())
> + if (num_online_cpus() < 2)
ditto
> + local_flush_tlb_all();
> + else if (riscv_use_sbi_for_rfence())
> sbi_remote_sfence_vma_asid(NULL, 0, FLUSH_TLB_MAX_SIZE, FLUSH_TLB_NO_ASID);
> else
> on_each_cpu(__ipi_flush_tlb_all, NULL, 1);
> --
> 2.42.0
>
>
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv
Powered by blists - more mailing lists