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AJvYcCWIVnQIa8/i0wnSC91tVKn+LFa7hKJD/TkI9TjvhldFkYdJcl0uctw328YpJsdd0kkuvgHElukqlg==@kvack.org X-Gm-Message-State: AOJu0YzNioFuLQeyyklCm0avaW9XjQKGbCEKVsxVzwd4deWVI3/DwHNO o1998gkrdbEG7z6h0jwkN8RRZS9BqrAKwNBdIIE4XQmMgn+6eOfxsVYo5c08/TMmmfHKg9aRyfD X23qa1fYjCMKl6ty63X9SVhp11H8= X-Gm-Gg: ASbGncsPyY3bTkN5L7KLz8T/3fEVyyTRjTt4ZuAMlSf/mxj+jWHYB/ijituLfS2FP7R ilZgxT9aMjwgmgVBVVyrBASueORgzf+S/ X-Google-Smtp-Source: AGHT+IFIf76/m18OY4g7R3eEd4MmZoeaqRE4i/4+NasxdugQcUeImn0repBSl/Tiwsk+0tJruMOcKU366rRUjjCoD5k= X-Received: by 2002:a17:906:3101:b0:a9a:dc3:c86e with SMTP id a640c23a62f3a-aa50990b1aamr6444766b.11.1732211309820; Thu, 21 Nov 2024 09:48:29 -0800 (PST) MIME-Version: 1.0 References: <20241119205529.3871048-1-bjohannesmeyer@gmail.com> <20241119205529.3871048-2-bjohannesmeyer@gmail.com> In-Reply-To: From: Brian Johannesmeyer Date: Thu, 21 Nov 2024 10:48:17 -0700 Message-ID: Subject: Re: [RFC v2 1/2] dmapool: Move pool metadata into non-DMA memory To: Christoph Hellwig Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org, Raphael Isemann , Cristiano Giuffrida , Herbert Bos , Greg KH , Keith Busch Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 7380C1C000C X-Stat-Signature: 5z1aftbenqokupj5y7ji48xkp6mjs767 X-Rspam-User: X-HE-Tag: 1732211245-660682 X-HE-Meta: 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 g36Np3pB 3n2d/eZ28PxPtdHI52Uf5S38qsX/kvTtTZcquOubnh0U8MoSLClCVKP1GIYPrE7bZM1Xd9yC9mHuGjN1agNM9rt3IjLLjDrO0/5xyq1hQY+iKKKxziJ469+pnqOYutHfK5TZdkmZEWGrLe/Xic24NXe0HBhXRjtWGSXgUx4otOyLz9UA5GU5whcwo5niM/vp8Qog+OBdS6ajPVlcKqvXyEedaae2HEOJdQgthLYR++5b/2rmsHk3NPCcWIJPdLYaK+nID3aIf+0g9XPC/OGsgVjZSUskyGpgO+6+3FkS6i2fACqJCkM7FoONkLY1gPCyfy91fveRMiv+fNSc/9SLG2pxsYFKezMT6RIIS+OFWEdXs6rITmBQKcjrzoIdW4L1930XT X-Bogosity: Ham, tests=bogofilter, spamicity=0.033563, 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 Wed, Nov 20, 2024 at 10:03=E2=80=AFPM Christoph Hellwig wrote: > Indeed. You'd probably need to split the linkage of the pages into > a list of those that have free blocks and those that don't as a minimum. > > Can you share your current version? Sure, I can share the current version, though fair warning---it=E2=80=99s still quite messy. FWIW, I wonder if the bitmap approach might be more suitable as a separate RFC. AFAICT, the primary issue with the currently submitted patches is their runtime overhead. I=E2=80=99ve proposed a way to address t= his in my recent response to [RFC v2 0/2]. Unfortunately, as I noted, improving the memory overhead without worsening the runtime performance is challenging---for example, removing the `next_block` pointers would require iterating over all pages to find a free `block`, which significantly impacts the runtime. That said, how would you prefer I share my bitmap approach? Should I submit it as a separate patch series or provide the patch directly in this thread? Thanks, Brian Johannesmeyer