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Mon, 6 Jul 2026 04:30:48 +0000 (GMT) Message-ID: <54d24191-efd1-418d-92df-20ca6d385675@linux.ibm.com> Date: Mon, 6 Jul 2026 10:00:47 +0530 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: Shrikanth Hegde 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-Authority-Analysis: v=2.4 cv=M7J97Sws c=1 sm=1 tr=0 ts=6a4b2f7e cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=IkcTkHD0fZMA:10 a=RAioF0-LDSMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=V8glGbnc2Ofi9Qvn3v5h:22 a=BSqJRU1AZdZnwssNLooA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNzA2MDAzOSBTYWx0ZWRfX/dpp6gHrOL8Q ChslzIk79ZVCMRzfLpInlLDWkx7RNV1tbge61i0UFL40DpRDFDhukWmlGM/JVqA84ro6MerZdAZ fZ8LvSZLZ6bEn3uc4AxAzwN8bEGv0WeR/J2boghGoT6OmqVuZvlCKf92PNC59/h3p86XlIkRCLn zSAtqw/WbYcueWZqmHhC79nZBy7XJ3eNx9l/P90xR2bW2mM3bk+QsDLmWxytVNZwMf+A0CQRerw KrY3hN5Nxz8JOfgPtJ6rtmgVpGOkiCxulu6T0N1py9rSXPSyllW2g5U+jLtMcDTMx38tFGKqr0s gCo69/NBRH3eYf6skinfWFGeBJ5bvsgEbEn4ol6DkfViwdGZeuyDFkIL6BXgFXiiDsufJEiQfgI BZvm0RIHiimkek4gk5zOa3iDUCXxTmp8/0jWQ8gOCRANsgqtxhxaQ+xVuDpH2WsoOOyKN9XEipP a7hmqJOVReCQxYmTqkQ== X-Proofpoint-Spam-Info: AW1haW4tMjYwNzA2MDAzOSBTYWx0ZWRfX2bh7peGdyi2q cg0CczwEpqUsdjoK9pmEE5+Tv1ZYNn3QhBbZnW+VUcjo9rSFXIvX8b12yhNW2r1oL7NoNfzSqNo 7aRhOiGdjK4P4EsOYIv/t1EpEQeaHkU= X-Proofpoint-GUID: 2CLjigsAJAaQ-4HHm1YJDi2fKiTlebBq X-Proofpoint-ORIG-GUID: FBi_OX143CeHoPKZIBhftYgVcO9t4LQc X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.125,FMLib:17.12.100.49 definitions=2026-07-05_02,2026-07-03_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 lowpriorityscore=0 malwarescore=0 clxscore=1015 adultscore=0 priorityscore=1501 bulkscore=0 spamscore=0 impostorscore=0 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2607060039 Hi Mark, On 7/3/26 7:03 PM, 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. This cleanup looks good indeed. little bit more cleanup can be added, details of it at the end. > > 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 Is this reversed? How come vmlinux is more whereas bzImage is less? > [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 > > Mark. > > Mark Rutland (5): > sched: dynamic: Make PREEMPT_DYNAMIC depend on ARCH_HAS_PREEMPT_LAZY > sched: dynamic: Simplify {cond,might}_resched() > sched: dynamic: Simplify preempt_schedule{,_notrace}() > sched: dynamic: Simplify irqentry_exit_cond_resched() > sched: dynamic: Remove HAVE_PREEMPT_DYNAMIC_{CALL,KEY} > > arch/Kconfig | 38 ------- > arch/arm64/Kconfig | 1 - > arch/arm64/include/asm/preempt.h | 10 -- > arch/loongarch/Kconfig | 1 - > arch/powerpc/Kconfig | 1 - > arch/powerpc/include/asm/preempt.h | 7 -- > arch/riscv/Kconfig | 1 - > arch/s390/Kconfig | 1 - > arch/s390/include/asm/preempt.h | 11 -- > arch/x86/Kconfig | 1 - > arch/x86/include/asm/preempt.h | 28 ----- > include/asm-generic/preempt.h | 10 -- > include/linux/irq-entry-common.h | 17 +-- > include/linux/kernel.h | 20 ---- > include/linux/sched.h | 31 +---- > kernel/Kconfig.preempt | 9 +- > kernel/entry/common.c | 17 +-- > kernel/sched/core.c | 176 +---------------------------- > 18 files changed, 13 insertions(+), 367 deletions(-) > Btw, I ran it on powerpc, builds and boots. Bloat-o-meter says, Total: Before=32286154, After=32267870, chg -0.06% In addition, I think you can also remove accessor methods of none, voluntary. I see preempt_model_none is used. (Though one may question its usage there). That wrapper can be outside of #ifdef as preempt dynamic can't choose none/voluntary. --- diff --git a/include/linux/preempt.h b/include/linux/preempt.h index d964f965c8ff..b4dd4fc13cf8 100644 --- a/include/linux/preempt.h +++ b/include/linux/preempt.h @@ -469,22 +469,9 @@ DEFINE_LOCK_GUARD_0(preempt, preempt_disable(), preempt_enable()) DEFINE_LOCK_GUARD_0(preempt_notrace, preempt_disable_notrace(), preempt_enable_notrace()) #ifdef CONFIG_PREEMPT_DYNAMIC - -extern bool preempt_model_none(void); -extern bool preempt_model_voluntary(void); extern bool preempt_model_full(void); extern bool preempt_model_lazy(void); - #else - -static inline bool preempt_model_none(void) -{ - return IS_ENABLED(CONFIG_PREEMPT_NONE); -} -static inline bool preempt_model_voluntary(void) -{ - return IS_ENABLED(CONFIG_PREEMPT_VOLUNTARY); -} static inline bool preempt_model_full(void) { return IS_ENABLED(CONFIG_PREEMPT); @@ -494,9 +481,16 @@ static inline bool preempt_model_lazy(void) { return IS_ENABLED(CONFIG_PREEMPT_LAZY); } - #endif +static inline bool preempt_model_none(void) +{ + return IS_ENABLED(CONFIG_PREEMPT_NONE); +} +static inline bool preempt_model_voluntary(void) +{ + return IS_ENABLED(CONFIG_PREEMPT_VOLUNTARY); +} static inline bool preempt_model_rt(void) { return IS_ENABLED(CONFIG_PREEMPT_RT); diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 9eb279eade26..59a8c8e63ca1 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -7815,8 +7815,6 @@ EXPORT_SYMBOL(__cond_resched_rwlock_write); enum { preempt_dynamic_undefined = -1, - preempt_dynamic_none, - preempt_dynamic_voluntary, preempt_dynamic_full, preempt_dynamic_lazy, }; @@ -7901,8 +7899,6 @@ static void __init preempt_dynamic_init(void) } \ EXPORT_SYMBOL_GPL(preempt_model_##mode) -PREEMPT_MODEL_ACCESSOR(none); -PREEMPT_MODEL_ACCESSOR(voluntary); PREEMPT_MODEL_ACCESSOR(full); PREEMPT_MODEL_ACCESSOR(lazy);