From: "Dmitry V. Levin" <ldv@altlinux.org>
To: ALT Linux kernel packages development <devel-kernel@lists.altlinux.org>
Subject: Re: [d-kernel] CONFIG_PREEMPT=y --> CONFIG_PREEMPT_VOLUNTARY=y
Date: Fri, 6 May 2022 21:49:15 +0300
Message-ID: <20220506184915.GA26339@altlinux.org> (raw)
In-Reply-To: <20220506153110.6wygefz343jvascg@altlinux.org>
On Fri, May 06, 2022 at 06:31:10PM +0300, Vitaly Chikunov wrote:
> On Fri, May 06, 2022 at 05:59:29PM +0300, Dmitry V. Levin wrote:
> > On Fri, May 06, 2022 at 05:54:49PM +0300, Vitaly Chikunov wrote:
> > > On Fri, May 06, 2022 at 05:53:06PM +0300, Vladimir D. Seleznev wrote:
> > > > On Fri, May 06, 2022 at 05:44:37PM +0300, Vitaly Chikunov wrote:
> > > >
> > > > > Предлагаю так же отключить нашу традиционную std-def опцию CONFIG_PREEMPT=y
> > > >
> > > > Вроде бы CONFIG_PREEMPT=y включен в un-def, а в std-def традиционно
> > > > выключен.
> > >
> > > Да это и имелось ввиду. Спасибо за поправку.
> >
> > Главное - не выключать CONFIG_PREEMPT_DYNAMIC.
>
> Это другой вариант о котором я не думал, но может стоит сделать и так.
>
> На сколько я понял, по умолчанию эта опция включает PREEMPT_NONE, а не
> PREEMPT_VOLUNTARY. То есть умолчание хуже чем CONFIG_PREEMPT_VOLUNTARY=y.
Давайте почитаем код вслух:
config PREEMPT_NONE
bool "No Forced Preemption (Server)"
select PREEMPT_NONE_BUILD if !PREEMPT_DYNAMIC
config PREEMPT_VOLUNTARY
bool "Voluntary Kernel Preemption (Desktop)"
depends on !ARCH_NO_PREEMPT
select PREEMPT_VOLUNTARY_BUILD if !PREEMPT_DYNAMIC
config PREEMPT
bool "Preemptible Kernel (Low-Latency Desktop)"
depends on !ARCH_NO_PREEMPT
select PREEMPT_BUILD
config PREEMPT_DYNAMIC
bool "Preemption behaviour defined on boot"
depends on HAVE_PREEMPT_DYNAMIC && !PREEMPT_RT
select JUMP_LABEL if HAVE_PREEMPT_DYNAMIC_KEY
select PREEMPT_BUILD
default y if HAVE_PREEMPT_DYNAMIC_CALL
static void __init preempt_dynamic_init(void)
{
if (preempt_dynamic_mode == preempt_dynamic_undefined) {
if (IS_ENABLED(CONFIG_PREEMPT_NONE)) {
sched_dynamic_update(preempt_dynamic_none);
} else if (IS_ENABLED(CONFIG_PREEMPT_VOLUNTARY)) {
sched_dynamic_update(preempt_dynamic_voluntary);
} else {
/* Default static call setting, nothing to do */
WARN_ON_ONCE(!IS_ENABLED(CONFIG_PREEMPT));
preempt_dynamic_mode = preempt_dynamic_full;
pr_info("Dynamic Preempt: full\n");
}
}
}
Получается, что PREEMPT_DYNAMIC по сути включает CONFIG_PREEMPT,
что соответствует preempt=full.
Похоже, что HAVE_PREEMPT_DYNAMIC_CALL включено по умолчанию только на x86*.
--
ldv
next prev parent reply other threads:[~2022-05-06 18:49 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-06 14:44 Vitaly Chikunov
2022-05-06 14:53 ` Vladimir D. Seleznev
2022-05-06 14:54 ` Vitaly Chikunov
2022-05-06 14:59 ` Dmitry V. Levin
2022-05-06 15:31 ` Vitaly Chikunov
2022-05-06 18:49 ` Dmitry V. Levin [this message]
2022-05-06 21:16 ` Vitaly Chikunov
2022-05-07 0:49 ` Vitaly Chikunov
2022-05-07 7:25 ` Dmitry V. Levin
2022-05-06 15:39 ` Andrey Savchenko
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