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Howlett" , akpm@linux-foundation.org, keescook@chromium.org, jannh@google.com, sroettger@google.com, willy@infradead.org, gregkh@linuxfoundation.org, torvalds@linux-foundation.org, usama.anjum@collabora.com, corbet@lwn.net, merimus@google.com, rdunlap@infradead.org, jeffxu@google.com, jorgelo@chromium.org, groeck@chromium.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, dave.hansen@intel.com, linux-hardening@vger.kernel.org, deraadt@openbsd.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Fri, Apr 19, 2024 at 2:22=E2=80=AFAM Jeff Xu wrote= : > The overhead is likely to grow linearly with the number of VMA, since > it takes time to retrieve VMA's metadata. > > Let's use one data sample to look at impact: > > Test: munmap 1000 memory range, each memory range has 1 VMA > > syscall__ vmas t t_mseal delta_ns per_vma % > munmap__ 1 909 944 35 35 104% > > For those 1000 munmap calls, sealing adds 35000 ns in total, or 35 ns per= call. Have you tried to spray around some likely() and unlikely()s? Does that make a difference? I'm thinking that sealing VMAs will be very rare, and mprotect/munmapping them is probably a programming error anyway, so the extra branches in the mprotect/munmap/madvice (etc) should be a nice target for some branch annotation. --=20 Pedro