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Mon, 06 Nov 2023 23:00:04 -0800 (PST) Received: from localhost ([12.44.203.122]) by smtp.gmail.com with ESMTPSA id kx14-20020a170902f94e00b001ca222edc16sm6950068plb.135.2023.11.06.23.00.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 06 Nov 2023 23:00:03 -0800 (PST) Date: Mon, 06 Nov 2023 23:00:03 -0800 (PST) X-Google-Original-Date: Mon, 06 Nov 2023 22:59:59 PST (-0800) Subject: Re: [PATCH v6 0/4] riscv: tlb flush improvements In-Reply-To: <24E0FC81-810E-44FD-9494-CA9374E495B5@gmail.com> CC: alexghiti@rivosinc.com, Will Deacon , aneesh.kumar@linux.ibm.com, akpm@linux-foundation.org, npiggin@gmail.com, peterz@infradead.org, mchitale@ventanamicro.com, vincent.chen@sifive.com, Paul Walmsley , aou@eecs.berkeley.edu, linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, samuel@sholland.org, prabhakar.csengg@gmail.com From: Palmer Dabbelt To: nadav.amit@gmail.com Message-ID: Mime-Version: 1.0 (MHng) Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 7366140020 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: hhrq4ut4uwitu9omohw1y5w3zcgu1u4w X-HE-Tag: 1699340406-214132 X-HE-Meta: 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 TK5Whkqw 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.002957, 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 Mon, 30 Oct 2023 07:01:48 PDT (-0700), nadav.amit@gmail.com wrote: > >> On Oct 30, 2023, at 3:30 PM, Alexandre Ghiti wrote: >> >> + on_each_cpu_mask(cmask, >> + __ipi_flush_tlb_range_asid, >> + &ftd, 1); >> > > Unrelated, but having fed Do you mean `ftd`? If so I'm not all that convinced that's a problem: sure it's 4x`long`, so we pass it on the stack instead of registers, but otherwise we'd need another `on_each_cpu_mask()` callback to shim stuff through via registers. > on the stack might cause it to be unaligned to > the cacheline, which in x86 we have seen introduces some overhead. We have 128-bit stack alignment on RISC-V, so the elements are at least aligned. Since they're just being loaded up as scalars for the next function call I'm not sure the alignment is all that exciting here. > Actually, it is best not to put it on the stack, if possible to reduce > cache traffic. Sorry if I'm just missing something, but I'm not convinced this is a measurable performance problem.