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Fri, 8 Mar 2024 05:23:26 +0000 (GMT) From: Vishal Chourasia To: peterz@infradead.org, linux-kernel@vger.kernel.org Cc: Vishal Chourasia Subject: [RFC 0/1] sched: Deprecate DOUBLE_TICK feature Date: Fri, 8 Mar 2024 10:53:03 +0530 Message-ID: <20240308052304.1835792-1-vishalc@linux.ibm.com> X-Mailer: git-send-email 2.44.0 X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: m0jjc0U45t03EhqeeBSCcmBUr-NEC51j X-Proofpoint-GUID: m0jjc0U45t03EhqeeBSCcmBUr-NEC51j Content-Transfer-Encoding: 8bit X-Proofpoint-UnRewURL: 0 URL was un-rewritten Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.272,Aquarius:18.0.1011,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2024-03-08_03,2024-03-06_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 phishscore=0 malwarescore=0 priorityscore=1501 mlxlogscore=790 impostorscore=0 adultscore=0 lowpriorityscore=0 mlxscore=0 spamscore=0 bulkscore=0 clxscore=1011 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2311290000 definitions=main-2403080040 Upon examining commit 5e963f2bd465, titled "sched/fair: Commit to EEVDF," it was noted that the method check_preempt_tick was removed. This change has rendered the DOUBLE_TICK feature, which previously played a role within the entity_tick function, inconsequential in the scheduling decisions. Historically, DOUBLE_TICK enabled periodic ticks to proceed even when a high-resolution timer (hrtick) was active, with the potential to cancel the hrtick timer in __schedule if it was active. With the removal of decision point where DOUBLE_TICK played a role by commit 5e963f2bd465, questions arise regarding its current utility. The discussion centers on whether there is a continued need for the hrtick timer as the system transitions towards EEVDF for calculating preemption points, based on entity lag, and as the scheduler manages resource allocation in quanta. Particularly, in scenarios involving multiple processes with different nice values, where EEVDF governs their preemption according to their lag, however the behavior depends on the specific values of base_slice_ns and config_hz. Link: https://lore.kernel.org/lkml/0818a331-cea3-4962-88ad-09bccbd3659d@linux.ibm.com/ Vishal Chourasia (1): sched: Deprecate DOUBLE_TICK feature kernel/sched/fair.c | 6 ------ kernel/sched/features.h | 1 - 2 files changed, 7 deletions(-) -- 2.43.0