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Wed, 1 Jan 2025 17:51:17 -0500 (EST) Date: Wed, 1 Jan 2025 17:51:16 -0500 From: Leo Famulari To: guix-devel@gnu.org Subject: Linux 6.12 new preemption models Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=103.168.172.158; envelope-from=leo@famulari.name; helo=fhigh-a7-smtp.messagingengine.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: guix-devel@gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: "Development of GNU Guix and the GNU System distribution." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: guix-devel-bounces+larch=yhetil.org@gnu.org Sender: guix-devel-bounces+larch=yhetil.org@gnu.org X-Migadu-Flow: FLOW_IN X-Migadu-Country: US X-Migadu-Scanner: mx11.migadu.com X-Migadu-Spam-Score: -7.22 X-Spam-Score: -7.22 X-Migadu-Queue-Id: 4DDC9954A7 X-TUID: 9Jtny+oKvXBI FYI, Linux / linux-libre 6.12 introduces a new set of preemption options: ------ Preemption Model 1. No Forced Preemption (Server) (PREEMPT_NONE) > 2. Voluntary Kernel Preemption (Desktop) (PREEMPT_VOLUNTARY) 3. Preemptible Kernel (Low-Latency Desktop) (PREEMPT) 4. Fully Preemptible Kernel (Real-Time) (PREEMPT_RT) (NEW) ------ These options trade between kernel throughput and latency. PREEMPT_NONE is how the kernels worked before 6.12. The trade-off made in PREEMPT_VOLUNTARY is suggested for desktops, so I'm going to select it for our 6.12 kernel packaging and it will presumably remain so for future versions as well. But if you are building Guix kernels for a busy server or HPC, you should select PREEMPT_NONE. And you might have use cases for the other options as well. Let me know if you disagree. References: https://cateee.net/lkddb/web-lkddb/PREEMPT_NONE.html https://cateee.net/lkddb/web-lkddb/PREEMPT_VOLUNTARY.html https://cateee.net/lkddb/web-lkddb/PREEMPT.html https://cateee.net/lkddb/web-lkddb/PREEMPT_RT.html