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[209.85.218.49]) by smtp.gmail.com with ESMTPSA id wy12-20020a170906fe0c00b0095f07223918sm4081309ejb.138.2023.04.28.09.08.38 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 28 Apr 2023 09:08:39 -0700 (PDT) Received: by mail-ej1-f49.google.com with SMTP id a640c23a62f3a-958bb7731a9so1432157566b.0 for ; Fri, 28 Apr 2023 09:08:38 -0700 (PDT) X-Received: by 2002:a17:907:988:b0:959:bbda:fa51 with SMTP id bf8-20020a170907098800b00959bbdafa51mr5254889ejc.41.1682698118661; Fri, 28 Apr 2023 09:08:38 -0700 (PDT) MIME-Version: 1.0 References: <20230427153345.451d86681f9c6775ea579e5a@linux-foundation.org> In-Reply-To: From: Linus Torvalds Date: Fri, 28 Apr 2023 09:08:21 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [GIT PULL] MM updates for 6.4-rc1 To: Suren Baghdasaryan Cc: Andrew Morton , mm-commits@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Lorenzo Stoakes , Vlastimil Babka Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: CEB28180015 X-Stat-Signature: 8cpjg5qayods98ypt3pbwha8zuy36meo X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1682698121-593039 X-HE-Meta: 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 Eh5co5nj 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 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: On Fri, Apr 28, 2023 at 9:03=E2=80=AFAM Suren Baghdasaryan wrote: > > I wanted these stats enabled by default to be able to identify > possible pathological cases and to also let users disable them if they > can't tolerate even a small overhead in the pagefault path. Should I > document this reasoning for the config option? You should document what the stats actually count (at a high enough level for a user to understand), and why anybody would want to keep them on. Honestly, 99% of the time, these are things that *developers* think they might want, but that nobody else will ever ever use. Really, ask yourself if a normal user would ever look at them? Now, ask yourself whether this might be something that a cloud provider would want to look at to gather statistics. And if it's the latter case, then it should be "default n", because the default should be for the people who DO NOT KNOW, AND DO NOT CARE. The cloud provider will be using a custom config anyway. The default is irrelevant for that use. The use that *matters* is literally the clueless end user who I bet will never look at these numbers, and will never be asked for them. Linus