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Hermes SMTP Server) with ESMTPA ID 9686c52ec99ca4522e39aaa35476498a; Tue, 03 Mar 2026 13:28:49 +0000 (UTC) Message-ID: Date: Tue, 3 Mar 2026 14:28:47 +0100 Precedence: bulk X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] ext4: rralloc - (former rotalloc) improved round-robin allocation policy Content-Language: hr To: Theodore Tso Cc: Andreas Dilger , libaokun1@huawei.com, adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, yangerkun@huawei.com, libaokun9@gmail.com References: <20260225201520.220071-1-mario_lohajner.ref@rocketmail.com> <20260225201520.220071-1-mario_lohajner@rocketmail.com> <20260226024819.GA39209@macsyma-wired.lan> <04dfeda0-8c13-4233-b631-d8912d4fe6f0@rocketmail.com> <20260227011200.GA68551@macsyma-wired.lan> <2af6328d-5a72-476d-9768-9398a9417ea6@rocketmail.com> <20260227164319.GB93969@macsyma-wired.lan> <20260303013309.GB6520@macsyma-wired.lan> From: Mario Lohajner In-Reply-To: <20260303013309.GB6520@macsyma-wired.lan> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Mailer: WebService/1.1.25198 mail.backend.jedi.jws.acl:role.jedi.acl.token.atz.jws.hermes.yahoo On 03. 03. 2026. 02:33, Theodore Tso wrote: > On Mon, Mar 02, 2026 at 09:04:44PM +0100, Mario Lohajner wrote: >> RRALLOC spreads allocation starting points across block groups to avoid >> repeated concentration under parallel load. > > There are already other ways in which we spread allocations across > block groups. You need to tell explain a specific workload where this > actually makes a difference. > > Also note that in most use cases, files are written once, and read > multiple times. So spreading blocks across different block groups is > can often be actively harmful. > >> In high-concurrency testing, performance is consistently comparable to >> or occasionally better than the regular allocator. No regressions have >> been observed across tested configurations. > > No regressions, and only "occasionally better" not enough of a justifiation. > > What is your real life workload which is motivating your efforts? > > - Ted RRALLOC targets sustained parallel overwrite-heavy workloads such as scratch disks, rendering outputs, database storage and VM image storage. It introduces a round-robin allocation policy across block groups to reduce short-term allocation concentration under high concurrency. It is not intended to improve write-once/read-many workloads and remains disabled by default. I do understand that without clearly measurable workload-specific improvement, this is likely not sufficient justification for upstream inclusion. I will continue evaluating and refining the allocator out-of-tree. If I am able to demonstrate concrete and reproducible benefits beyond allocation geometry and occasional contention-related effects, I will revisit the discussion with additional data. Thank you for the review and valuable feedback. Regards, Mario Lohajner