From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2114D1A718 for ; Wed, 3 Jan 2024 15:10:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Tp7oRgzy" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5E6BEC433C8; Wed, 3 Jan 2024 15:10:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1704294640; bh=NkRRzJNtkIaqD3FKoHNbeRWvalOUr4JWu2/1EIqaoKg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Tp7oRgzysGa93W3YGZKULOpHNoDKsXBqBy7chiOvQRihBgJAypspwLbYkCRdMiPS1 CG2X/bi28oBBjMJHWtgVvI62dmPslcmBad0n8Pbi/SSbAjHtVk6TRZv935ARL7q6oM vax735NBXLFbcWKHhd4LlzguyudA7vws5JovhRyOFYNwdRSI+aEoqs73RZApf6Em2s jHX0dEp9SRH8GF/4vXA/HVrRoXsmyrEPU9v0IsyLLWD3CxgcflqJ8imWZunQyfM8KZ LOLlWOcdGlDfjBpcKFsym0/Nzet30kg3hM8pkILeE01GnkyOGInXsc8j3HYsmqfKPs EDq1ZBCvZqcKw== Date: Wed, 3 Jan 2024 22:57:58 +0800 From: Jisheng Zhang To: Samuel Holland Cc: Palmer Dabbelt , linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Alexandre Ghiti Subject: Re: [PATCH v4 04/12] riscv: Only send remote fences when some other CPU is online Message-ID: References: <20240102220134.3229156-1-samuel.holland@sifive.com> <20240102220134.3229156-5-samuel.holland@sifive.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20240102220134.3229156-5-samuel.holland@sifive.com> 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 > --- > > 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@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-riscv