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[149.14.88.26]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4771e387aa9sm53806965e9.4.2025.10.29.09.19.54 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 29 Oct 2025 09:19:55 -0700 (PDT) Message-ID: <2bff49c4-6292-446b-9cd4-1563358fe3b4@redhat.com> Date: Wed, 29 Oct 2025 17:19:54 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: Bug: Performance regression in 1013af4f585f: mm/hugetlb: fix huge_pmd_unshare() vs GUP-fast race To: Jann Horn , Lorenzo Stoakes Cc: "Uschakow, Stanislav" , "linux-mm@kvack.org" , "trix@redhat.com" , "ndesaulniers@google.com" , "nathan@kernel.org" , "akpm@linux-foundation.org" , "muchun.song@linux.dev" , "mike.kravetz@oracle.com" , "liam.howlett@oracle.com" , "osalvador@suse.de" , "vbabka@suse.cz" , "stable@vger.kernel.org" References: <4d3878531c76479d9f8ca9789dc6485d@amazon.de> <81d096fb-f2c2-4b26-ab1b-486001ee2cac@lucifer.local> <4ebbd082-86e3-4b86-bb01-6325f300fc9c@lucifer.local> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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I started hacking on this (only found a bit of time this week), and in essence, we'll be using the mmu_gather when unsharing to collect the pages and handle the TLB flushing etc. (TLB flushing in that hugetlb area is a mess) It almost looks like a cleanup. Having that said, it will take a bit longer to finish it and, of course, I first have to test it then to see if it even works. But it looks doable. :) -- Cheers David / dhildenb