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Hermes SMTP Server) with ESMTPA ID fe1b15f879a7cba06976c78243764d51; Mon, 02 Mar 2026 20:04:47 +0000 (UTC) Message-ID: Date: Mon, 2 Mar 2026 21:04:44 +0100 Precedence: bulk X-Mailing-List: linux-kernel@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> From: Mario Lohajner In-Reply-To: <20260227164319.GB93969@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 27. 02. 2026. 17:43, Theodore Tso wrote: > On Fri, Feb 27, 2026 at 03:46:59PM +0100, Mario Lohajner wrote: >> >> Concentrated allocation can create contention, write amplification, and >> uneven LBA utilization even on modern NVMe/SSD devices. > > Uneven LBA utilization is the thing where I'm asking, "why should we care". > > In terms of how this would cause contention and write amplification, > <>. What is your benchmarks where you can > demonstrate this, and how common is this across NVMe/SSD devices? > That is, if it's just one trashy product, maybe it should just be > avoided --- especially if it has other problems. > > - Ted RRALLOC spreads allocation starting points across block groups to avoid repeated concentration under parallel load. This reduces short-term allocation concentration in the same regions when multiple CPUs allocate concurrently. In high-concurrency testing, performance is consistently comparable to or occasionally better than the regular allocator. No regressions have been observed across tested configurations. Under sustained parallel allocation pressure, testing shows improved tail-latency stability compared to the current allocator. Additional high-concurrency test results are available at: https://github.com/mlohajner/RRALLOC Regards, Mario Lohajner