From: "Arnd Bergmann" <arnd@arndb.de>
To: "Peter Zijlstra" <peterz@infradead.org>,
"John Paul Adrian Glaubitz" <glaubitz@physik.fu-berlin.de>
Cc: "Matthew Wilcox" <willy@infradead.org>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Linus Torvalds" <torvalds@linux-foundation.org>,
"Ankur Arora" <ankur.a.arora@oracle.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org,
"Andrew Morton" <akpm@linux-foundation.org>,
"Andy Lutomirski" <luto@kernel.org>,
"Borislav Petkov" <bp@alien8.de>,
"Dave Hansen" <dave.hansen@linux.intel.com>,
"H. Peter Anvin" <hpa@zytor.com>,
"Ingo Molnar" <mingo@redhat.com>,
juri.lelli@redhat.com,
"Vincent Guittot" <vincent.guittot@linaro.org>,
"Mel Gorman" <mgorman@suse.de>,
"Steven Rostedt" <rostedt@goodmis.org>,
jon.grimm@amd.com, bharata@amd.com, raghavendra.kt@amd.com,
"Boris Ostrovsky" <boris.ostrovsky@oracle.com>,
"Konrad Rzeszutek Wilk" <konrad.wilk@oracle.com>,
"Juergen Gross" <jgross@suse.com>,
andrew.cooper3@citrix.com,
"Geert Uytterhoeven" <geert@linux-m68k.org>,
linux-m68k@lists.linux-m68k.org,
"Richard Weinberger" <richard@nod.at>,
"Anton Ivanov" <anton.ivanov@cambridgegreys.com>,
"Johannes Berg" <johannes@sipsolutions.net>,
linux-um@lists.infradead.org, "Brian Cain" <bcain@quicinc.com>,
linux-hexagon@vger.kernel.org,
"Richard Henderson" <richard.henderson@linaro.org>,
"Ivan Kokshaysky" <ink@jurassic.park.msu.ru>,
"Matt Turner" <mattst88@gmail.com>,
linux-alpha@vger.kernel.org
Subject: Re: Arches that don't support PREEMPT
Date: Thu, 21 Sep 2023 08:20:38 -0400 [thread overview]
Message-ID: <020d4d23-ee7e-49aa-9ed5-1bde21fd0a5d@app.fastmail.com> (raw)
In-Reply-To: <20230919141627.GB39281@noisy.programming.kicks-ass.net>
On Tue, Sep 19, 2023, at 10:16, Peter Zijlstra wrote:
> On Tue, Sep 19, 2023 at 03:48:09PM +0200, John Paul Adrian Glaubitz wrote:
>> On Tue, 2023-09-19 at 15:42 +0200, Peter Zijlstra wrote:
>> > > The agreement to kill off ia64 wasn't an invitation to kill off other stuff
>> > > that people are still working on! Can we please not do this?
>> >
>> > If you're working on one of them, then surely it's a simple matter of
>> > working on adding CONFIG_PREEMPT support :-)
>>
>> As Geert poined out, I'm not seeing anything particular problematic with the
>> architectures lacking CONFIG_PREEMPT at the moment. This seems to be more
>> something about organizing KConfig files.
>
> The plan in the parent thread is to remove PREEMPT_NONE and
> PREEMPT_VOLUNTARY and only keep PREEMPT_FULL.
...
>
> PREEMPT isn't something new. Also, I don't think the arch part for
> actually supporting it is particularly hard, mostly it is sticking the
> preempt_schedule_irq() call in return from interrupt code path.
>
> If you convert the arch to generic-entry (a much larger undertaking)
> then you get this for free.
I checked the default configurations for both in-kernel targets and
general-purpose distros and was surprised to learn that very few
actually turn on full preemption by default:
- All distros I looked at (rhel, debian, opensuse) use PREEMPT_VOLUNTARY
by default, though they usually also set PREEMPT_DYNAMIC to let users
override it at boot time.
- The majority (220) of all defconfig files in the kernel don't select
any preemption options, and just get PREEMPT_NONE automatically.
This includes the generic configs for armv7, s390 and mips.
- A small number (24) set PREEMPT_VOLUNTARY, but this notably
includes x86 and ppc64. x86 is the only one of those that sets
PREEMPT_DYNAMIC
- CONFIG_PREEMPT=y (full preemption) is used on 89 defconfigs,
including arm64 and a lot of the older arm32, arc and
mips platforms.
If we want to have a chance of removing both PREEMPT_NONE and
PREEMPT_VOLUNTARY, I think we should start with changing the
defaults first, so defconfigs that don't specify anything else
get PREEMPT=y, and distros that use PREEMPT_VOLUNTARY use it
use it in the absence of a command line argument. If that
doesn't cause too many regressions, the next step might be
to hide the choice under CONFIG_EXPERT until all m68k and
alpha no longer require PREEMPT_NONE.
Arnd
next prev parent reply other threads:[~2023-09-21 17:05 UTC|newest]
Thread overview: 152+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-30 18:49 [PATCH v2 0/9] x86/clear_huge_page: multi-page clearing Ankur Arora
2023-08-30 18:49 ` [PATCH v2 1/9] mm/clear_huge_page: allow arch override for clear_huge_page() Ankur Arora
2023-08-30 18:49 ` [PATCH v2 2/9] mm/huge_page: separate clear_huge_page() and copy_huge_page() Ankur Arora
2023-08-30 18:49 ` [PATCH v2 3/9] mm/huge_page: cleanup clear_/copy_subpage() Ankur Arora
2023-09-08 13:09 ` Matthew Wilcox
2023-09-11 17:22 ` Ankur Arora
2023-08-30 18:49 ` [PATCH v2 4/9] x86/clear_page: extend clear_page*() for multi-page clearing Ankur Arora
2023-09-08 13:11 ` Matthew Wilcox
2023-08-30 18:49 ` [PATCH v2 5/9] x86/clear_page: add clear_pages() Ankur Arora
2023-08-30 18:49 ` [PATCH v2 6/9] x86/clear_huge_page: multi-page clearing Ankur Arora
2023-08-31 18:26 ` kernel test robot
2023-09-08 12:38 ` Peter Zijlstra
2023-09-13 6:43 ` Raghavendra K T
2023-08-30 18:49 ` [PATCH v2 7/9] sched: define TIF_ALLOW_RESCHED Ankur Arora
2023-09-08 7:02 ` Peter Zijlstra
2023-09-08 17:15 ` Linus Torvalds
2023-09-08 22:50 ` Peter Zijlstra
2023-09-09 5:15 ` Linus Torvalds
2023-09-09 6:39 ` Ankur Arora
2023-09-09 9:11 ` Peter Zijlstra
2023-09-09 20:04 ` Ankur Arora
2023-09-09 5:30 ` Ankur Arora
2023-09-09 9:12 ` Peter Zijlstra
2023-09-09 20:15 ` Ankur Arora
2023-09-09 21:16 ` Linus Torvalds
2023-09-10 3:48 ` Ankur Arora
2023-09-10 4:35 ` Linus Torvalds
2023-09-10 10:01 ` Ankur Arora
2023-09-10 18:32 ` Linus Torvalds
2023-09-11 15:04 ` Peter Zijlstra
2023-09-11 16:29 ` andrew.cooper3
2023-09-11 17:04 ` Ankur Arora
2023-09-12 8:26 ` Peter Zijlstra
2023-09-12 12:24 ` Phil Auld
2023-09-12 12:33 ` Matthew Wilcox
2023-09-18 23:42 ` Thomas Gleixner
2023-09-19 1:57 ` Linus Torvalds
2023-09-19 8:03 ` Ingo Molnar
2023-09-19 8:43 ` Ingo Molnar
2023-09-19 13:43 ` Thomas Gleixner
2023-09-19 13:25 ` Thomas Gleixner
2023-09-19 12:30 ` Thomas Gleixner
2023-09-19 13:00 ` Arches that don't support PREEMPT Matthew Wilcox
2023-09-19 13:34 ` Geert Uytterhoeven
2023-09-19 13:37 ` John Paul Adrian Glaubitz
2023-09-19 13:42 ` Peter Zijlstra
2023-09-19 13:48 ` John Paul Adrian Glaubitz
2023-09-19 14:16 ` Peter Zijlstra
2023-09-19 14:24 ` John Paul Adrian Glaubitz
2023-09-19 14:32 ` Matthew Wilcox
2023-09-19 15:31 ` Steven Rostedt
2023-09-20 14:38 ` Anton Ivanov
2023-09-21 12:20 ` Arnd Bergmann [this message]
2023-09-19 14:17 ` Thomas Gleixner
2023-09-19 14:50 ` H. Peter Anvin
2023-09-19 14:57 ` Matt Turner
2023-09-19 17:09 ` Ulrich Teichert
2023-09-19 17:25 ` Linus Torvalds
2023-09-19 17:58 ` John Paul Adrian Glaubitz
2023-09-19 18:31 ` Thomas Gleixner
2023-09-19 18:38 ` Steven Rostedt
2023-09-19 18:52 ` Linus Torvalds
2023-09-19 19:53 ` Thomas Gleixner
2023-09-20 7:32 ` Ingo Molnar
2023-09-20 7:29 ` Ingo Molnar
2023-09-20 8:26 ` Thomas Gleixner
2023-09-20 10:37 ` David Laight
2023-09-19 14:21 ` Anton Ivanov
2023-09-19 15:17 ` Thomas Gleixner
2023-09-19 15:21 ` Anton Ivanov
2023-09-19 16:22 ` Richard Weinberger
2023-09-19 16:41 ` Anton Ivanov
2023-09-19 17:33 ` Thomas Gleixner
2023-10-06 14:51 ` Geert Uytterhoeven
2023-09-20 14:22 ` [PATCH v2 7/9] sched: define TIF_ALLOW_RESCHED Ankur Arora
2023-09-20 20:51 ` Thomas Gleixner
2023-09-21 0:14 ` Thomas Gleixner
2023-09-21 0:58 ` Ankur Arora
2023-09-21 2:12 ` Thomas Gleixner
2023-09-20 23:58 ` Thomas Gleixner
2023-09-21 0:57 ` Ankur Arora
2023-09-21 2:02 ` Thomas Gleixner
2023-09-21 4:16 ` Ankur Arora
2023-09-21 13:59 ` Steven Rostedt
2023-09-21 16:00 ` Linus Torvalds
2023-09-21 22:55 ` Thomas Gleixner
2023-09-23 1:11 ` Thomas Gleixner
2023-10-02 14:15 ` Steven Rostedt
2023-10-02 16:13 ` Thomas Gleixner
2023-10-18 1:03 ` Paul E. McKenney
2023-10-18 12:09 ` Ankur Arora
2023-10-18 17:51 ` Paul E. McKenney
2023-10-18 22:53 ` Thomas Gleixner
2023-10-18 23:25 ` Paul E. McKenney
2023-10-18 13:16 ` Thomas Gleixner
2023-10-18 14:31 ` Steven Rostedt
2023-10-18 17:55 ` Paul E. McKenney
2023-10-18 18:00 ` Steven Rostedt
2023-10-18 18:13 ` Paul E. McKenney
2023-10-19 12:37 ` Daniel Bristot de Oliveira
2023-10-19 17:08 ` Paul E. McKenney
2023-10-18 17:19 ` Paul E. McKenney
2023-10-18 17:41 ` Steven Rostedt
2023-10-18 17:59 ` Paul E. McKenney
2023-10-18 20:15 ` Ankur Arora
2023-10-18 20:42 ` Paul E. McKenney
2023-10-19 0:21 ` Thomas Gleixner
2023-10-19 19:13 ` Paul E. McKenney
2023-10-20 21:59 ` Paul E. McKenney
2023-10-20 22:56 ` Ankur Arora
2023-10-20 23:36 ` Paul E. McKenney
2023-10-21 1:05 ` Ankur Arora
2023-10-21 2:08 ` Paul E. McKenney
2023-10-24 12:15 ` Thomas Gleixner
2023-10-24 18:59 ` Paul E. McKenney
2023-09-23 22:50 ` Thomas Gleixner
2023-09-24 0:10 ` Thomas Gleixner
2023-09-24 7:19 ` Matthew Wilcox
2023-09-24 7:55 ` Thomas Gleixner
2023-09-24 10:29 ` Matthew Wilcox
2023-09-25 0:13 ` Ankur Arora
2023-10-06 13:01 ` Geert Uytterhoeven
2023-09-19 7:21 ` Ingo Molnar
2023-09-19 19:05 ` Ankur Arora
2023-10-24 14:34 ` Steven Rostedt
2023-10-25 1:49 ` Steven Rostedt
2023-10-26 7:50 ` Sergey Senozhatsky
2023-10-26 12:48 ` Steven Rostedt
2023-09-11 16:48 ` Steven Rostedt
2023-09-11 20:50 ` Linus Torvalds
2023-09-11 21:16 ` Linus Torvalds
2023-09-12 7:20 ` Peter Zijlstra
2023-09-12 7:38 ` Ingo Molnar
2023-09-11 22:20 ` Steven Rostedt
2023-09-11 23:10 ` Ankur Arora
2023-09-11 23:16 ` Steven Rostedt
2023-09-12 16:30 ` Linus Torvalds
2023-09-12 3:27 ` Matthew Wilcox
2023-09-12 16:20 ` Linus Torvalds
2023-09-19 3:21 ` Andy Lutomirski
2023-09-19 9:20 ` Thomas Gleixner
2023-09-19 9:49 ` Ingo Molnar
2023-08-30 18:49 ` [PATCH v2 8/9] irqentry: define irqentry_exit_allow_resched() Ankur Arora
2023-09-08 12:42 ` Peter Zijlstra
2023-09-11 17:24 ` Ankur Arora
2023-08-30 18:49 ` [PATCH v2 9/9] x86/clear_huge_page: make clear_contig_region() preemptible Ankur Arora
2023-09-08 12:45 ` Peter Zijlstra
2023-09-03 8:14 ` [PATCH v2 0/9] x86/clear_huge_page: multi-page clearing Mateusz Guzik
2023-09-05 22:14 ` Ankur Arora
2023-09-08 2:18 ` Raghavendra K T
2023-09-05 1:06 ` Raghavendra K T
2023-09-05 19:36 ` Ankur Arora
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