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AJvYcCWzkRx6zyFFiQ+rMDukdCAnbGCfOOGTro8um616K0UjOODei8+GkuWskyYf4AowYWl/NV03sMOLXA==@kvack.org X-Gm-Message-State: AOJu0YxfZFkRNOQVfFaMv3Apu1w77Yp7QIHH7yD8s5JFj1x8d/9ol0gd TRbZXpWBU9BH6i5FUxbdy9dRionfBvmB9DaztLgoD0MQAIQth92SVt7wdOnqtaEiuaOWnk5xDQE m8LAiaMvMvxQnQJVe3f03rwL4LgtiwJo= X-Gm-Gg: ASbGncsvbfHM0BhJwOdJcpGU7BySWcGJS469WJIIAwecZwzFvacJJHaVgxCbyk3fOi2 8SwIdyABCgte45Eqoy3YAEyX1Prrfk/mHRkoPqkx55kyV0dXMg/KM7PwCzbdIjpCwnkaQcDBd3V c8ZDoPZdf/N4cUk8clnHZzmyYb+tpa5LGmzuHNRq1NRH2k X-Google-Smtp-Source: AGHT+IEu0wvQ5rhdA7BJLa2LTFM56TLWJzqwagC9Vg/DVegxmBIqU65ZnQ+yPR7TraWX6oDXCxLvKV4jW7/+CnRcrpk= X-Received: by 2002:a05:6102:c89:b0:4e2:86e8:3188 with SMTP id ada2fe7eead31-4e6e473792bmr1885640137.0.1748591560495; Fri, 30 May 2025 00:52:40 -0700 (PDT) MIME-Version: 1.0 References: <85778a76-7dc8-4ea8-8827-acb45f74ee05@lucifer.local> <20250529211423.GA1271329@cmpxchg.org> In-Reply-To: <20250529211423.GA1271329@cmpxchg.org> From: Barry Song <21cnbao@gmail.com> Date: Fri, 30 May 2025 19:52:28 +1200 X-Gm-Features: AX0GCFtLq2Vrtv-b7fSZ_FGTqJuT5ElgRYnChnL5uE5cw7If3ZrbkNFfQmhEunI Message-ID: Subject: Re: [DISCUSSION] proposed mctl() API To: Johannes Weiner Cc: Matthew Wilcox , Lorenzo Stoakes , Andrew Morton , Shakeel Butt , "Liam R . Howlett" , David Hildenbrand , Vlastimil Babka , Jann Horn , Arnd Bergmann , Christian Brauner , SeongJae Park , Usama Arif , Mike Rapoport , linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, Pedro Falcato Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: B6CCB4000D X-Stat-Signature: j7cm7ig3r44bo5pouwi6xe5jijk3boxc X-Rspam-User: X-HE-Tag: 1748591561-850730 X-HE-Meta: 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 MCsFefu2 ANuACarVpVRXNi8Om3RceJKEDy4pDAOX31MeSm6baolSyx3/5ZkkVQqkY44IQsbpCURJM+BPGpnHibw5uT5MuO7U/KNA9o1DfCWQCZ2DMp3iPQOokzh7zCb/RbKSQdRpBcIkdo4InSABClzkAqny2oebfw9sK57iZFNaFvtbf1x+igL5Op7EwzOoE/y1N4M8BgWM0jz52X2hy6wnG+y0YtxWvMce9qt+7Ik6slBDxI580Tg+94YJACSycRBLWjOaID2Ae9NKQh2EMxNUPGCRcKSX5fVC16Nz5iZfD7QLKuNDleFACxFEp9o55pOWQc1+U0X0IRG37O/uEjeqiA9JDS/USon1SmVJ35IHHzlKv6cgNLilkj+qflMr6QmytOAkWYU2aFPXV4lkbJ6b4R3KhWKg5sqGz8eeG+EMFTArFzAAjFHw= 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: On Fri, May 30, 2025 at 9:14=E2=80=AFAM Johannes Weiner wrote: > > On Thu, May 29, 2025 at 04:28:46PM +0100, Matthew Wilcox wrote: > > Barry's problem is that we're all nervous about possibly regressing > > performance on some unknown workloads. Just try Barry's proposal, see > > if anyone actually compains or if we're just afraid of our own shadows. > > I actually explained why I think this is a terrible idea. But okay, I > tried the patch anyway. > > This is 'git log' on a hot kernel repo after a large IO stream: > > VANILLA BARRY > Real time 49.93 ( +0.00%) 60.36 ( +20.48%) > User time 32.10 ( +0.00%) 32.09 ( -0.04%) > System time 14.41 ( +0.00%) 14.64 ( +1.50%) > pgmajfault 9227.00 ( +0.00%) 18390.00 ( +99.30%) > workingset_refault_file 184.00 ( +0.00%) 236899.00 (+127954.05%) > > Clearly we can't generally ignore page cache hits just because the > mmaps() are intermittent. Hi Johannes, Thanks! Are you on v1, which lacks folio demotion[1], or v2, which includes it [2]? [1] https://lore.kernel.org/linux-mm/20250412085852.48524-1-21cnbao@gmail.c= om/ [2] https://lore.kernel.org/linux-mm/20250514070820.51793-1-21cnbao@gmail.c= om/ > > The whole point is to cache across processes and their various > apertures into a common, long-lived filesystem space. > > Barry knows something about the relationship between certain processes > and certain files that he could exploit with MADV_COLD-on-exit > semantics. But that's not something the kernel can safely assume. Not > without defeating the page cache for an entire class of file accesses. Best Regards Barry