From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 585CBFED3CC for ; Fri, 24 Apr 2026 13:37:10 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id C46DA6B00A6; Fri, 24 Apr 2026 09:37:09 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id C1F0F6B00A7; Fri, 24 Apr 2026 09:37:09 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B0D296B00A9; Fri, 24 Apr 2026 09:37:09 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 9D6976B00A6 for ; Fri, 24 Apr 2026 09:37:09 -0400 (EDT) Received: from smtpin14.hostedemail.com (lb01b-stub [10.200.18.250]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 4B45C140195 for ; Fri, 24 Apr 2026 13:37:09 +0000 (UTC) X-FDA: 84693550578.14.1538B05 Received: from mail-qk1-f173.google.com (mail-qk1-f173.google.com [209.85.222.173]) by imf19.hostedemail.com (Postfix) with ESMTP id 848191A0014 for ; Fri, 24 Apr 2026 13:37:07 +0000 (UTC) Authentication-Results: imf19.hostedemail.com; dkim=pass header.d=soleen.com header.s=google header.b=FvSWv3st; spf=pass (imf19.hostedemail.com: domain of pasha.tatashin@soleen.com designates 209.85.222.173 as permitted sender) smtp.mailfrom=pasha.tatashin@soleen.com; dmarc=pass (policy=reject) header.from=soleen.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1777037827; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=uWWbj/VPS78zqXVF7C00n2rbNCSFE3WHczyNV5IMoNo=; b=cX7uRQjWYiIqkYlBay8wOD6QQ/CU7k1WTzTUnNz3gAdsAwDPzKd2F/d12MZ3/9yZVS8XI0 6VNY9KAnHxH0x7eDT39I9Httl/PBqOjAZ4n1HgU33GcMlLNjb6ZydEyMo14HBHOW9JkFAX najDd+I1TGzXQXgbhRyfsIVsppJxbxM= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1777037827; a=rsa-sha256; cv=none; b=VIsGPVwWzFWU3Gv9y7hvC1mjx7yixKmhTOQIMJZ054uiSjZPclG773OGkD02bgFLEUhidM dh3osc1AMTKElyw7bTXsmcia9qCqPsJJ0VP4tlrydMzc5B7kdFRtIcpYJrXt4Fy3Xt6238 CiRDd9Ry+Kp8IKQtkUsSNLx5M+o2VvA= ARC-Authentication-Results: i=1; imf19.hostedemail.com; dkim=pass header.d=soleen.com header.s=google header.b=FvSWv3st; spf=pass (imf19.hostedemail.com: domain of pasha.tatashin@soleen.com designates 209.85.222.173 as permitted sender) smtp.mailfrom=pasha.tatashin@soleen.com; dmarc=pass (policy=reject) header.from=soleen.com Received: by mail-qk1-f173.google.com with SMTP id af79cd13be357-8f231f3b130so88746085a.3 for ; Fri, 24 Apr 2026 06:37:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=soleen.com; s=google; t=1777037827; x=1777642627; darn=kvack.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=uWWbj/VPS78zqXVF7C00n2rbNCSFE3WHczyNV5IMoNo=; b=FvSWv3sttOhquhwO+I/7XjDvKEjp6szkD+qOgRN9zI5ep5UlCqWoKv2QVauCuVkmwO 8jLhZdwTNwZzcg88+w/5g7xzcX898YPLhvFcQai7lckB6cVZOMVd01/1Bf/vWR/KKezs DUndxMGiQFurWWXe/Ws5+/htMCeET/vVokEpsECmMRmDynSHcWHW4L85f0uwYXCb7x8c oilVf4/atwwE3HRNLlhdV3Bb+uuXGL632jxrr4NT+0oamAURu9Qkd8SX2OxFLyumRVHB gMJNQF8lbUifiel0cym2RYBi6mN3ioi1/izzatHqEPFzUfN/uOyAY2D5j9bfWVHqhymJ 0Fiw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1777037827; x=1777642627; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-gg:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=uWWbj/VPS78zqXVF7C00n2rbNCSFE3WHczyNV5IMoNo=; b=csXNWfIOsErwbvxwc8id3kJXNz7ej3e2APp0mp/z80+BRh+MYtKDw60xAb/4iwXwNN f/Iqg6ryK2SVdpCw/AOq5lTOL6ElmxQz3jLxJVjNkALsWEgCc88xKdngcbj62hGbRQnX uhiOVW4dW/anvXWGf3SK4bAAJKJNRGrBLc3JPrs2Y28U7XszSc3bcJC/hpQm2EmyY9pM krAH3k1XPkGBPPbOndMLfw8YDauiKp+MPmWlQLpvazGICwfmU7lmtf54NWfH44mCJDuN FGqo4iNEXsoEBrCtt5SsbrSDDa0q34TnB3hwdneW7+E32rhWypg3qSng+Dv+q15l5VYL v+SQ== X-Forwarded-Encrypted: i=1; AFNElJ8wQdZ/eC/HEs+XwD+1r0Jz7PyTSBHa0j832+H+iBqxevVHOlTbgd6Lktmkf1QYLZAB93YC69JApQ==@kvack.org X-Gm-Message-State: AOJu0YyMxrPgDef1qv92PHHEfKuwR9DR+f68BWQwbJKVJ0sUijKbh1Pg UbwFUjxSnfedaRCkq32bGcA3nnQaalgVwI2ioPYFXF/YZlbRPWuR4jdcnYh4XPmkg2o= X-Gm-Gg: AeBDiet7krLl26CGN29k8TxFs0J/ufEhEABOM40wLHrs/dhuiATGKcCJ+AlcIbcTlVl plmsE8K57e26caioMId1oIRoi7ENqUk02l4+PJvw3igXmnefwQG3OtdvP1PTGAfliFhhUhKKPwV VGIDtkldHDfOpHd1Tk2yb63r6Q1BzwkcVMC8jDwg0G59dd1DajHLyNVUAr7hfoU8UmF23rsRmKB pH4MH3PhQ9NZSfu+VZdYM6B2+Z/KrCa7mhdoKidLf/ZMIeoUiZxGBznsAlz9vESIivlEtkTcdgH cpBfAbJTzsYqnD+Lx1O/ht1MWAG+aPxxC+BKYG2MZ6d2xBHn1PVOMWeEpm4WOeuytSP1Iyyv7RU pO1PNkuwBWITADSuzUTMTZszzGeUASngprTawLI4qIRI46xoTq3P7iJIc9Ug7OJ04xt3odeBuak n5+XZORO+oMmI9m152Tq4k25J23viVhHOLRdtlmVUo2+i4wd6GgvkFZAvwdM+iZQ== X-Received: by 2002:a05:620a:17a3:b0:8d0:27b8:fb7 with SMTP id af79cd13be357-8e79246cd79mr4470598685a.46.1777037826446; Fri, 24 Apr 2026 06:37:06 -0700 (PDT) Received: from plex ([71.181.43.54]) by smtp.gmail.com with ESMTPSA id af79cd13be357-8e7d5fe98dcsm1992846185a.7.2026.04.24.06.37.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 24 Apr 2026 06:37:06 -0700 (PDT) Date: Fri, 24 Apr 2026 13:37:04 +0000 From: Pasha Tatashin To: Andrew Morton Cc: Lance Yang , peterz@infradead.org, david@kernel.org, dave.hansen@intel.com, dave.hansen@linux.intel.com, ypodemsk@redhat.com, hughd@google.com, will@kernel.org, aneesh.kumar@kernel.org, npiggin@gmail.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, arnd@arndb.de, ljs@kernel.org, ziy@nvidia.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, shy828301@gmail.com, riel@surriel.com, jannh@google.com, jgross@suse.com, seanjc@google.com, pbonzini@redhat.com, boris.ostrovsky@oracle.com, virtualization@lists.linux.dev, kvm@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, ioworker0@gmail.com, roman.gushchin@linux.dev Subject: Re: [PATCH 7.2 v10 0/2] skip redundant sync IPIs when TLB flush sent them Message-ID: References: <20260424062528.71951-1-lance.yang@linux.dev> <20260424063024.ce42ee6a5546e4d9337dd007@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260424063024.ce42ee6a5546e4d9337dd007@linux-foundation.org> X-Stat-Signature: zm6p7g5g74pqd1xio6u6mec4cru3tf8q X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 848191A0014 X-Rspam-User: X-HE-Tag: 1777037827-849475 X-HE-Meta: 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 Y3FdvHb2 WzPI/YsB55yedF7q2aCpZAoFFni2MJadju56hnMF7+QUNDtSIQrFf0noBYm4SWPBsKsYdd5oLthWUniNqcmv7klNVWKr/0srWwKRQ1UYlaQJaiaSZd4aCSqan/FjzE44p1jR/QClF52QBuh27XD8s3CcnQbnSkl0oov9RbsndEr7k9Q1yOTQJzsFxm5R54/Tm8/IF1TNMXVnf+XHdkd+cLf+Xgl16PKjLTYV3uGzPOVyKM2qGKYu4nxHoPNUuQNrubbmUZIR27cH0IgV7vncz2ieziJ8yH+yFQEvSV6Gv1dJjZ7K/L0/PLaSyXhZpuLyKdk+044oyMvttz1w+X/MkVh7U9MB2+y9NSscSXzd5tHSwKpNjrJZ46pye2Q== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 04-24 06:30, Andrew Morton wrote: > On Fri, 24 Apr 2026 14:25:26 +0800 Lance Yang wrote: > > > When page table operations require synchronization with software/lockless > > walkers, they call tlb_remove_table_sync_{one,rcu}() after flushing the > > TLB (tlb->freed_tables or tlb->unshared_tables). > > > > On architectures where the TLB flush already sends IPIs to all target CPUs, > > the subsequent sync IPI broadcast is redundant. This is not only costly on > > large systems where it disrupts all CPUs even for single-process page table > > operations, but has also been reported to hurt RT workloads[1]. > > > > This series introduces tlb_table_flush_implies_ipi_broadcast() to check if > > the prior TLB flush already provided the necessary synchronization. When > > true, the sync calls can early-return. > > > > A few cases rely on this synchronization: > > > > 1) hugetlb PMD unshare[2]: The problem is not the freeing but the reuse > > of the PMD table for other purposes in the last remaining user after > > unsharing. > > > > 2) khugepaged collapse[3]: Ensure no concurrent GUP-fast before collapsing > > and (possibly) freeing the page table / re-depositing it. > > Sashiko questions: > https://sashiko.dev/#/patchset/20260424062528.71951-1-lance.yang@linux.dev > > (I never know if my Sashiko emails are welcome/useful. Maybe Sashiko > said the same stuff about v9 and it's all wrong. But better safe than > sorry!) These emails are helpful; but, I do not believe you should have to manually follow up with a link to every new patch series. Perhaps Sashiko could automatically send a summary email in response to the cover letter, or provide a link once the reviews are complete. For the kexec ML, we opted-in with Roman to receive automated emails from sashiko. +Cc: Roman. > >