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Howlett" To: Lokesh Gidra Cc: akpm@linux-foundation.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, selinux@vger.kernel.org, surenb@google.com, kernel-team@android.com, aarcange@redhat.com, peterx@redhat.com, david@redhat.com, axelrasmussen@google.com, bgeffon@google.com, willy@infradead.org, jannh@google.com, kaleshsingh@google.com, ngeoffray@google.com, timmurray@google.com, rppt@kernel.org Subject: Re: [PATCH v2 0/3] per-vma locks in userfaultfd Message-ID: <20240129203904.7dcugltsjajldlea@revolver> Mail-Followup-To: "Liam R. 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 QU1i+jbT 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We can use per-vma locks instead to significantly reduce > the contention issue. Is this really an issue? I'm surprised so much userfaultfd work is happening to create contention. Can you share some numbers and how your patch set changes the performance? > > Changes since v1 [1]: > - rebase patches on 'mm-unstable' branch > > [1] https://lore.kernel.org/all/20240126182647.2748949-1-lokeshgidra@google.com/ > > Lokesh Gidra (3): > userfaultfd: move userfaultfd_ctx struct to header file > userfaultfd: protect mmap_changing with rw_sem in userfaulfd_ctx > userfaultfd: use per-vma locks in userfaultfd operations > > fs/userfaultfd.c | 86 ++++--------- > include/linux/userfaultfd_k.h | 75 ++++++++--- > mm/userfaultfd.c | 229 ++++++++++++++++++++++------------ > 3 files changed, 229 insertions(+), 161 deletions(-) > > -- > 2.43.0.429.g432eaa2c6b-goog > >