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AJvYcCXZ+u5f+AdnHYdvv3cjAi0RhVh8HnaJHSvY34rciBSqL5s1Q4WN/xwneTTjg/Y9etsFFG17CD/6Vw==@kvack.org X-Gm-Message-State: AOJu0YyGxbdyJMImj4FkabpEQSaqqcHjCc3ddRJGMXxJ43EkaXwTP2Du T1egtP7gZMZLoEFBZE8K2jb9Ue57XA3vyYJ9Q3ieODgF+gZGhKM6ae0JC2lA1LzL7WEYQGoQzkd AHCFQHtoA4wkTUtWhX2UH6lYxeoB7g25oCzZS X-Gm-Gg: ASbGncunY28hbQxO1lrvbFEuYIestcLi759P9pgi/X4KIN7HcGK7oCY7VyDsdWIeGsZ m0knWcdW9pwRQKYDYMrbQGjQ0Yw+ELkIkZiBz9Q== X-Google-Smtp-Source: AGHT+IE47hFmYSXjIUPDMFKlc5R0VSjP/hrFbf+J0DNX6VXzImARZkb63ga3Mdl4kfh18yLKTpqRLqube80Uksah1q8= X-Received: by 2002:ac8:7dcc:0:b0:466:91fd:74c4 with SMTP id d75a77b69052e-46c87d08ee2mr7068141cf.0.1736641918411; Sat, 11 Jan 2025 16:31:58 -0800 (PST) MIME-Version: 1.0 References: <20250111042604.3230628-1-surenb@google.com> <20250111042604.3230628-11-surenb@google.com> <20250111063152.1638-1-hdanton@sina.com> <20250111121320.1656-1-hdanton@sina.com> <20250111234502.1739-1-hdanton@sina.com> In-Reply-To: <20250111234502.1739-1-hdanton@sina.com> From: Suren Baghdasaryan Date: Sat, 11 Jan 2025 16:31:47 -0800 X-Gm-Features: AbW1kvYDUzlTQKrjj7u1mj5niBxAejKHpdDkFb3h0uueXdU6HFyDWSL_ImAEarU Message-ID: Subject: Re: [PATCH v9 10/17] refcount: introduce __refcount_{add|inc}_not_zero_limited To: Hillf Danton Cc: akpm@linux-foundation.org, peterz@infradead.org, willy@infradead.org, hannes@cmpxchg.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Vlastimil Babka Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: AA1B240010 X-Stat-Signature: i3y3som1ykzghadk8nzu1gu1u9phyw3m X-Rspam-User: X-HE-Tag: 1736641919-134679 X-HE-Meta: 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 c3bk/d4n wC5liPIPCZxwldLnnkwVCth3r4cQS4UGHx31NJjShOm438SddLsdr/33yTqx4xMVz7gg9hZMAElFx5rKvpO4RPE3fNDUT9SbljC1xN/iRn1JnhB4vf1YjAyGQ/p2xxiDqlD2kAhwPEPAbbtfVDlDL2t5VTYB3A/7QO1nDang7iIkEMtmeToaJD6amF2EUIqk4tAoilRY59lMoTZyZ6tXPnSC/cmVSgWN+/6ziTuNHSpMGxd28V4QDsvFpwJOg2Mj0OcfRozKlnwoatYHteFaeytvtNRybSzn2JRmC X-Bogosity: Ham, tests=bogofilter, spamicity=0.121043, 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 Sat, Jan 11, 2025 at 3:45=E2=80=AFPM Hillf Danton wro= te: > > On Sat, 11 Jan 2025 09:11:52 -0800 Suren Baghdasaryan > > I see your point. I think it's a strong argument to use atomic > > directly instead of refcount for this locking. I'll try that and see > > how it looks. Thanks for the feedback! > > > Better not before having a clear answer to why is it sane to invent > anything like rwsem in 2025. What, the 40 bytes? Nope it is the > fair price paid for finer locking granuality. It's not just about the 40 bytes. It allows us to fold the separate vma->detached flag nicely into the same refcounter, which consolidates the vma state in one place. Later that makes it much easier to add SLAB_TYPESAFE_BY_RCU because now we have to preserve only this refcounter during the vma reuse. > > BTW Vlastimil, the cc list is cut down because I have to walk around > the spam check on the mail agent side. >