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AJvYcCXVbOTyi2d4OtyJwtEB0yAGzCpWeDmXqB8QrFbN3p4WFoxoOvcrwr8d6T3mBZ6rDed7yyznajSLqw==@kvack.org X-Gm-Message-State: AOJu0YwVCdwT8EvywAJi+JcGxqzrrVWatVY3aBFz6Hl4HtNMKhi3E7IN iLfuyzS7HsX9HuRcn9SnuEb7Y9yxmLhPmDhvd3w1G4owrlCA2BeiCH21zNBErcCToo4LUw0d86R 0UncKM7TPJX3UIVJUh9wEHy9b8DE= X-Google-Smtp-Source: AGHT+IFuIzzkQ+aYhNsqrwuq62kan4xtPQvwQfRQIyymgXebs0Fas5ZkvAOPaRjozaVR8s+SIeciuEovhswzVCTQFMQ= X-Received: by 2002:a17:90a:6984:b0:2e0:a4ce:108c with SMTP id 98e67ed59e1d1-2e1e63c1750mr12218257a91.40.1728320727891; Mon, 07 Oct 2024 10:05:27 -0700 (PDT) MIME-Version: 1.0 References: <20241001225207.2215639-1-andrii@kernel.org> <20241001225207.2215639-2-andrii@kernel.org> In-Reply-To: <20241001225207.2215639-2-andrii@kernel.org> From: Andrii Nakryiko Date: Mon, 7 Oct 2024 10:05:15 -0700 Message-ID: Subject: Re: [PATCH v2 tip/perf/core 1/5] mm: introduce mmap_lock_speculation_{start|end} To: akpm@linux-foundation.org, willy@infradead.org, mhocko@kernel.org, vbabka@suse.cz, linux-mm@kvack.org Cc: linux-trace-kernel@vger.kernel.org, peterz@infradead.org, oleg@redhat.com, rostedt@goodmis.org, mhiramat@kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, jolsa@kernel.org, paulmck@kernel.org, surenb@google.com, mjguzik@gmail.com, brauner@kernel.org, jannh@google.com, mingo@kernel.org, Andrii Nakryiko , Liam Howlett Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 4B207160019 X-Stat-Signature: kdoppmrixxmioumot3e7jwszphst4tot X-Rspam-User: X-HE-Tag: 1728320729-780674 X-HE-Meta: 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 UillziI0 eTHkrD7gDByEIkCEwQFkfBnKs5geJ33EJDzeylEHAwnijtkguRzA/k1NwVAozUdNe/9ywJchwKqfx6iU/xeVAs1zSRuLWn1jcZsPXYirf7WVgQl2RQPJhytJXbMjPOB2eNt0yv5xeoHJusmiYOQOCJOKfh46x+1FYZLZl4E31xiP13LkM1BMvz0Dyj5NuxmOZnoQb3kz2yk/1PIwOOATkk9jsefCGcFBzZu+a7VHQYcnUspZGnA5ebp4FMoYQed27ff7jJaoNlxiJeY0vZs3mz02gRuWmXtuXVrsnjayu0NIXgyc/o77uek76GZ3PRYF28Q6wq1wRhcznE2AibqGcqE03yxdxnhist+iyOVW3QzI8gzbjtXtE7F19YjumH9gqXxdN7SYemAt8lfwy+Zs4GGwws5iZpHBjF2B6cfXXApJ4vWJHq0PVFkB0o5uhOVkRKPxERWHTXSlvvRVIfwlzN5Z06ZiU1IMbDdVMF5+NfYa5A+oLsTJx7hb0ND7MNkwd56RC 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: +cc Liam, sorry, seems like I forgot to add you to the entire patch set on initial submission. On Tue, Oct 1, 2024 at 3:52=E2=80=AFPM Andrii Nakryiko = wrote: > > From: Suren Baghdasaryan > > Add helper functions to speculatively perform operations without > read-locking mmap_lock, expecting that mmap_lock will not be > write-locked and mm is not modified from under us. > > Suggested-by: Peter Zijlstra > Signed-off-by: Suren Baghdasaryan > Signed-off-by: Andrii Nakryiko > Link: https://lore.kernel.org/bpf/20240912210222.186542-1-surenb@google.c= om > --- > include/linux/mm_types.h | 3 ++ > include/linux/mmap_lock.h | 72 ++++++++++++++++++++++++++++++++------- > kernel/fork.c | 3 -- > 3 files changed, 63 insertions(+), 15 deletions(-) > Are memory-management folks OK with these changes? It would be nice to get some acks, if so, and I'd include it into respin, fixing minor things in uprobe patches. Thank you! Note, while this is initially needed for uprobe functionality, having an ability to quickly change whether mm_struct changed inbetween some speculative querying is generally useful functionality, and I believe it would help eliminating mmap_lock usage from /proc/PID/maps code. Which is a great outcome for everyone, as that mmap_lock can be quite disruptive in production workloads. So please don't see it as some irrelevant uprobe-related requirement, the applicability of this is much wider. [...]