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Sat, 06 Dec 2025 11:53:16 -0800 (PST) X-Google-Smtp-Source: AGHT+IH2aPGE6vYb1dltrITpg8eumtVfZJj4Id5GKymqQwmguys9MRcgGbHoYX1yIz3YPyGVGfbLsw== X-Received: by 2002:a05:7023:b01:b0:11b:d4a8:d24d with SMTP id a92af1059eb24-11e03260ecamr2282813c88.12.1765050796257; Sat, 06 Dec 2025 11:53:16 -0800 (PST) Received: from syn-2600-6c64-4e7f-603b-9b92-b2ac-3267-27e9.biz6.spectrum.com ([2600:6c64:4e7f:603b:9b92:b2ac:3267:27e9]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-11df7703bd7sm35128784c88.10.2025.12.06.11.53.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 06 Dec 2025 11:53:15 -0800 (PST) Message-ID: <6640379f1ef7e9305b77d1e322b04d9534a3fff5.camel@redhat.com> Subject: Re: [PATCH v1 0/4] mm/hugetlb: fixes for PMD table sharing (incl. using mmu_gather) From: Laurence Oberman To: "David Hildenbrand (Red Hat)" , linux-kernel@vger.kernel.org Cc: linux-arch@vger.kernel.org, linux-mm@kvack.org, Will Deacon , "Aneesh Kumar K.V" , Andrew Morton , Nick Piggin , Peter Zijlstra , Arnd Bergmann , Muchun Song , Oscar Salvador , "Liam R. Howlett" , Lorenzo Stoakes , Vlastimil Babka , Jann Horn , Pedro Falcato , Rik van Riel , Harry Yoo , Prakash Sangappa , Nadav Amit Date: Sat, 06 Dec 2025 14:53:02 -0500 In-Reply-To: <20251205213558.2980480-1-david@kernel.org> References: <20251205213558.2980480-1-david@kernel.org> User-Agent: Evolution 3.40.4 (3.40.4-11.el9_6.1) MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 1WuJf6EPsToq5o5Ev1Ej-_MLdpRNWmRoJR7bMDnsQQ8_1765050797 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 163D8160015 X-Stat-Signature: y9sme944wekz88bqwwmf89sx1bo545mi X-Rspam-User: X-HE-Tag: 1765050801-606344 X-HE-Meta: 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 IIPKzDqD 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 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 Fri, 2025-12-05 at 22:35 +0100, David Hildenbrand (Red Hat) wrote: > One functional fix, one performance regression fix, and two related > comment fixes. > > I cleaned up my prototype I recently shared [1] for the performance > fix, > deferring most of the cleanups I had in the prototype to a later > point. > While doing that I identified the other things. > > The goal of this patch set is to be backported to stable trees > "fairly" > easily. At least patch #1 and #4. > > Patch #1 fixes hugetlb_pmd_shared() not detecting any sharing > Patch #2 + #3 are simple comment fixes that patch #4 interacts with. > Patch #4 is a fix for the reported performance regression due to > excessive > IPI broadcasts during fork()+exit(). > > The last patch is all about TLB flushes, IPIs and mmu_gather. > Read: complicated > > I added as much comments + description that I possibly could, and I > am > hoping for review from Jann. > > There are plenty of cleanups in the future to be had + one reasonable > optimization on x86. But that's all out of scope for this series. > > Compile tested on plenty of architectures. > > Runtime tested, with a focus on fixing the performance regression > using > the original reproducer [2] on x86. > > I'm still busy with more testing (making sure that my TLB flushing > changes > are good), but sending this out already so people can test and review > while I am soon heading for LPC. > > [1] > https://lore.kernel.org/all/8cab934d-4a56-44aa-b641-bfd7e23bd673@kernel.org/ > [2] > https://lore.kernel.org/all/8cab934d-4a56-44aa-b641-bfd7e23bd673@kernel.org/ > > Cc: Will Deacon > Cc: "Aneesh Kumar K.V" > Cc: Andrew Morton > Cc: Nick Piggin > Cc: Peter Zijlstra > Cc: Arnd Bergmann > Cc: Muchun Song > Cc: Oscar Salvador > Cc: "Liam R. Howlett" > Cc: Lorenzo Stoakes > Cc: Vlastimil Babka > Cc: Jann Horn > Cc: Pedro Falcato > Cc: Rik van Riel > Cc: Harry Yoo > Cc: Uschakow, Stanislav" > Cc: Laurence Oberman > Cc: Prakash Sangappa > Cc: Nadav Amit > > David Hildenbrand (Red Hat) (4): >   mm/hugetlb: fix hugetlb_pmd_shared() >   mm/hugetlb: fix two comments related to huge_pmd_unshare() >   mm/rmap: fix two comments related to huge_pmd_unshare() >   mm/hugetlb: fix excessive IPI broadcasts when unsharing PMD tables >     using mmu_gather > >  include/asm-generic/tlb.h |  69 +++++++++++++++++++- >  include/linux/hugetlb.h   |  21 ++++--- >  mm/hugetlb.c              | 129 ++++++++++++++++++++---------------- > -- >  mm/mmu_gather.c           |   6 ++ >  mm/mprotect.c             |   2 +- >  mm/rmap.c                 |  45 +++++++------ >  6 files changed, 178 insertions(+), 94 deletions(-) > For the Series passed generic testing with a focus on the CVE regression and looks good. Tested-by: Laurence Oberman