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spf=pass (imf25.hostedemail.com: domain of ying.huang@linux.alibaba.com designates 115.124.30.132 as permitted sender) smtp.mailfrom=ying.huang@linux.alibaba.com; dmarc=pass (policy=none) header.from=linux.alibaba.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1761182532; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=2IDMW7CBAbRVu3DReKyJ3tXIFVRCpnWKhvXJ2ha+0SM=; b=YpCyJxkEuzn2IT9pCQCRhChNEgpPdnTutyes3+h4Hu9lgXpGMys8K6wMny7t6o87gNMgRX DrZLD0u/Oja2J/xZsFhaxRErmdQ9j2Mt9MgntDUet+SzogJILUZLvtKFWoKhg8SLDQPhiz 1G/ePAW52ntOQHPCwYsRb7vDNYOgoAs= DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1761182528; h=From:To:Subject:Date:Message-ID:MIME-Version:Content-Type; bh=2IDMW7CBAbRVu3DReKyJ3tXIFVRCpnWKhvXJ2ha+0SM=; b=hg9t7M7yFy76BfnX8wwq797179BQ5U/alsEYSDuMkFPIyd+anAJeXr+PhPVp1tCYIBw3s0a7QBQVWDhr/jsf37JMxg1A4+orIpQOsa7bvyuoYuMA0t60iTtGqYDI/RyNfvghAHzl2BvfsWpGVXpTQgDTiqS/oo5jMYFV/NMeTtA= Received: from DESKTOP-5N7EMDA(mailfrom:ying.huang@linux.alibaba.com fp:SMTPD_---0WqooiVd_1761182526 cluster:ay36) by smtp.aliyun-inc.com; Thu, 23 Oct 2025 09:22:07 +0800 From: "Huang, Ying" To: Barry Song <21cnbao@gmail.com> Cc: Catalin Marinas , Will Deacon , Andrew Morton , David Hildenbrand , Lorenzo Stoakes , Vlastimil Babka , Zi Yan , Baolin Wang , Ryan Roberts , Yang Shi , "Christoph Lameter (Ampere)" , Dev Jain , Anshuman Khandual , Yicong Yang , Kefeng Wang , Kevin Brodsky , Yin Fengwei , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH -v2 2/2] arm64, tlbflush: don't TLBI broadcast if page reused in write fault In-Reply-To: (Barry Song's message of "Wed, 22 Oct 2025 23:52:23 +1300") References: <20251013092038.6963-1-ying.huang@linux.alibaba.com> <20251013092038.6963-3-ying.huang@linux.alibaba.com> <87a51jfl44.fsf@DESKTOP-5N7EMDA> <871pmv9unr.fsf@DESKTOP-5N7EMDA> <875xc78es0.fsf@DESKTOP-5N7EMDA> <87a51j6zg7.fsf@DESKTOP-5N7EMDA> <87ms5j4444.fsf@DESKTOP-5N7EMDA> Date: Thu, 23 Oct 2025 09:22:05 +0800 Message-ID: <87qzuu1kg2.fsf@DESKTOP-5N7EMDA> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Stat-Signature: 7w5pez11fs15xmtkqtaifgcmcx4mgons X-Rspamd-Queue-Id: 9773AA000A X-Rspamd-Server: rspam09 X-HE-Tag: 1761182531-61081 X-HE-Meta: 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 hd9GFRPl fXQ+BhPj6JXQO3OYonjIiMCfNm7myk/6+v3G6L/EotxIdS++95Um7Ay1YdVfC2vF9nWd0riI9lk3XeghfAM3yQuSLZuWLAdJ0Z7sxdJAJRvrY/jBNs7ejkwahHewjKEFcshBCONwLO4KiJAfe+CSFdbJaISJirXfoad1kv0rzE0oVhYAZiQxwhoswVJq2t38e8KHrau+e8nekqLFUbkTFkrZqhvsSucbJtlTvZUZAzAmQTOADNFoPIEzZa+cyUdjm2so3HUsUuUqtl6qI3mm54DJOE9Snuug4byMYvpl+sEmShsOFmV9zkzssGw== 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: Barry Song <21cnbao@gmail.com> writes: > On Wed, Oct 22, 2025 at 11:34=E2=80=AFPM Huang, Ying > wrote: >> >> Barry Song <21cnbao@gmail.com> writes: >> >> > On Wed, Oct 22, 2025 at 10:46=E2=80=AFPM Huang, Ying >> > wrote: >> > >> >> > >> >> > I agree. Yet the ish barrier can still avoid the page faults during= CPU0's PTL. >> >> >> >> IIUC, you think that dsb(ish) compared with dsb(nsh) can accelerate >> >> memory writing (visible to other CPUs). TBH, I suspect that this is = the >> >> case. >> > >> > Why? In any case, nsh is not a smp domain. >> >> I think dsb(ish) will be slower than dsb(nsh) in theory. I guess that >> dsb just wait for the memory write to be visible in the specified >> shareability domain instead of making write faster. >> >> > I believe a dmb(ishst) is sufficient to ensure that the new PTE writes >> > are visible >> >> dmb(ishst) (smp_wmb()) should pair with dmb(ishld) (smp_rmb()). >> >> > to other CPUs. I=E2=80=99m not quite sure why the current flush code u= ses dsb(ish); >> > it seems like overkill. >> >> dsb(ish) here is used for tlbi(XXis) broadcast. It waits until the page >> table change is visible to the page table walker of the remote CPU. > > It seems we=E2=80=99re aligned on all points[1], although I=E2=80=99m not= sure whether > you have data comparing A and B. > > A: > write pte > don't broadcast pte > tlbi > don't broadcast tlbi > > with > > B: > write pte > broadcast pte I suspect that pte will be broadcast, DVM broadcast isn't used for the memory coherency IIUC. > tlbi > don't broadcast tlbi > > I guess the gain comes from "don't broadcat tlbi" ? > With B, we should be able to share many existing code. Ryan has some plan to reduce the code duplication with the current solution. > [1] > https://lore.kernel.org/linux-mm/20251013092038.6963-1-ying.huang@linux.a= libaba.com/T/#m54312d4914c69aa550bee7df36711c03a4280c52 --- Best Regards, Huang, Ying