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b=Gf9pQ/af33jkPwdM/5tgbvWGyNx5or7NiLzSPLWPf/matHojty611C2q3ZtsjVOA5 QGiLsSxw1vprazFYFKlVLl3DOAjlfoI5DTBnPD1gslBO0GG8otzapjEODkd38l1+wy JMkxhWV4XNqOa8gSM5l/Zw5UdwxMObagUzzhwH6jrhgTgxmBmW4Ohz/mrrZZ4ABLA1 ubxUvmNSoIrplgsvtklkilJ3mIbnx7U86nDXpy7jd9RHjqaORsLdeZLG5tzCYb5hFM ow+nweFB/PNpNryc3J+5jWGjflt8MsLSfCcrJPrOSt8DI67hYqdd9YbL8QrjtZeNNg BATC0icqBPBCQ== Date: Wed, 3 Jan 2024 23:04:04 +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> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 4D18420002 X-Stat-Signature: kypqzs64gtb1u8qfjzo7nxp57nrgxshg X-Rspam-User: X-HE-Tag: 1704295010-442521 X-HE-Meta: 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 TsFNBzuo y08ielZr+WLhUXMhV2RqlKywYSDKakbl93b/lK/I5zUdrxo4TIiGmvNAMxsGFMqT+4XK8vMLNFN4xf5gpDCofh7xs988YOyjokd8IExNK3bnPytT/D0fWvLuMAVFZNJFIxQxH6qY0VIJ2x3xofN3CiHsoGafs2FoQ/VVeVzO4trAE6giiaQtxenrDeZDdU62gNn9n09fA7kMbPyzHCoWBMqXDO0emtq2P1NcWOYya3K3jtzlvWrYAAxhjWjCIWdw3yv8wNaBLEGBJsYVsmdIAYMfVcyJ8qW4/CBt4FLm8hSITgZU= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Jan 03, 2024 at 10:58:01PM +0800, Jisheng Zhang wrote: > 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) aha, plz ignore this comment, I see the num_online_cpus() is defined as 1U for UP. > > 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