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Thu, 30 Jul 2026 15:39:12 +0000 (GMT) Received: from [9.224.76.67] (unknown [9.224.76.67]) by smtpav01.fra02v.mail.ibm.com (Postfix) with ESMTP; Thu, 30 Jul 2026 15:39:12 +0000 (GMT) Message-ID: <10c3cc66-080b-4a70-979d-90594b06d71d@linux.ibm.com> Date: Thu, 30 Jul 2026 17:39:12 +0200 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 0/5] sched: dynamic: Simplify PREEMPT_DYNAMIC To: Mark Rutland , linux-kernel@vger.kernel.org Cc: frederic@kernel.org, jstultz@google.com, juri.lelli@redhat.com, mingo@redhat.com, peterz@infradead.org, tglx@linutronix.de, vincent.guittot@linaro.org, vschneid@redhat.com References: <20260703133358.698078-1-mark.rutland@arm.com> Content-Language: en-US From: Mete Durlu In-Reply-To: <20260703133358.698078-1-mark.rutland@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-Spam-Info: AW1haW4tMjYwNzMwMDExNiBTYWx0ZWRfXwMsO0vZVi27M oZDPVO5tAZZ3nRx2WcgueHAb+3MgVVEpRgAGkwvOcFnACXRqumBmDVCstYd425DsijFEqGa+JOY kYDGKOZgRSQY2bLwLu/sctKKEoKPQxU= X-Proofpoint-GUID: NJemTpiwMXMOZ_2wp4fMSQhdwhaMGfrQ X-Proofpoint-ORIG-GUID: YX0jWFNMjQmXNSUpJPioxNNHnOM5mUhH X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNzMwMDExNiBTYWx0ZWRfX245iD092EwY/ PjoVaRd5ihZ5Dfu0i2urpciNxi7BOJ9NyyFz+jaalh0SidQVY0KaaSjoQIisUqfDF/VinyUECaI tRekG4yHfmT3ujYHPX89lAGC0ZrzyUqcMC34T0TNRJ9Hlqn9pwiDC7WFRi1zZNJNlNe4/YO816J R9HS+chqmHqWS4QwrZeePxSQfZLoQFwZx42d33MWTaRj0h/yg2ROxoKbG0tDNAdmEV6z/UCu8je i7KpNepHQyIi5epJqOeHWa8SLjaJJeD+0wUw9ZkrjdVcnmusvuXWvqrrQf9HI/4dZ+l1ogQOi71 UazoFuhlCuY+GYZOKETmcsChI4CEv+PN4VcaBKZJ0vPr1fpv6U5uN9eGj7/Dg/DJMlrkKJf1YYb +N3hiiir2Q1JQ05lg4Kp+2QeFvWatOHH6cNnhTuXJX+YhSfjG5uq4nTmJD9LgDAvi9JfvigPTnp PPWz5kBSyIflQ3UmgaA== X-Authority-Analysis: v=2.4 cv=X5Vi7mTe c=1 sm=1 tr=0 ts=6a6b7024 cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=IkcTkHD0fZMA:10 a=RAioF0-LDSMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=Y2IxJ9c9Rs8Kov3niI8_:22 a=5dd4K7wZ1E4D1jxyZCsA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-07-30_04,2026-07-29_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1011 impostorscore=0 lowpriorityscore=0 phishscore=0 priorityscore=1501 malwarescore=0 spamscore=0 suspectscore=0 bulkscore=0 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2607300116 On 03/07/2026 15:33, Mark Rutland wrote: > All architectures which currently suppoort PREEMPT_DYNAMIC select > ARCH_HAS_PREEMPT_LAZY. On architectures which select > ARCH_HAS_PREEMPT_LAZY, it has not been possible to select the NONE and > VOLUNTARY preemption models since v7.0 due to commit: > > 7dadeaa6e851 ("sched: Further restrict the preemption modes") > > Hence in practice PREEMPT_DYNAMIC no longer supports the NONE or > VOLUNTARY preemption models. > > This series makes the de-facto situation official by making > PREEMPT_DYNAMIC depend on ARCH_HAS_PREEMPT_LAZY, and removing all the > redundant code. Hi, I got some results for s390. > For x86_64 v7.2-rc1 defconfig built with GCC 10.2.1, this makes the > bzImage 28K smaller, mostly due to removing NOPs that will never be > patched to {cond,might}_resched() at runtime: > > [mark@lakrids:~/src/linux]% ls -al vmlinux-* > -rwxr-xr-x 1 mark mark 53844952 Jul 3 14:09 vmlinux-after > -rwxr-xr-x 1 mark mark 53842856 Jul 3 14:09 vmlinux-before > [mark@lakrids:~/src/linux]% ls -al bzImage-* > -rw-r--r-- 1 mark mark 14771200 Jul 3 14:09 bzImage-after > -rw-r--r-- 1 mark mark 14799872 Jul 3 14:08 bzImage-before > I applied the series over e4de1b9cb3b5 ("powerpc/dt_cpu_ftrs: Set CPU_FTR_P11_PVR for Power11 and later processors") I did git clean -xfd in between compiles and here is how it looks like for s390; vmlinux is almost 1M smaller $ ls -la before/vmlinux -rwxrwxr-x 1 meted meted 409306880 Jul 30 15:40 before/vmlinux $ ls -la after/vmlinux -rwxrwxr-x 1 meted meted 407987680 Jul 30 15:43 after/vmlinux $ bloat-o-meter before/vmlinux after/vmlinux add/remove: 67/50 grow/shrink: 731/2058 up/down: 54992/-161849 (-106857) bzImage is ~32K smaller $ ls -la before/bzImage -rwxrwxr-x 1 meted meted 12914688 Jul 30 15:24 before/bzImage $ ls -la after/bzImage -rwxrwxr-x 1 meted meted 12881920 Jul 30 15:30 after/bzImage I also did some sniff tests to see if it causes any behavior changes, not that its expected, didn't see anything.