From: Peter Zijlstra <peterz@infradead.org>
To: Valentin Schneider <valentin.schneider@arm.com>
Cc: "Barry Song" <21cnbao@gmail.com>,
LKML <linux-kernel@vger.kernel.org>,
LAK <linux-arm-kernel@lists.infradead.org>,
linux-ia64@vger.kernel.org, linux-mips@vger.kernel.org,
linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
linux-s390@vger.kernel.org, linux-sh@vger.kernel.org,
sparclinux@vger.kernel.org,
"Aubrey Li" <aubrey.li@linux.intel.com>,
"Barry Song" <song.bao.hua@hisilicon.com>,
"Tim Chen" <tim.c.chen@linux.intel.com>,
"Jonathan Cameron" <jonathan.cameron@huawei.com>,
"Russell King" <linux@armlinux.org.uk>,
"Catalin Marinas" <catalin.marinas@arm.com>,
"Will Deacon" <will@kernel.org>,
"Thomas Bogendoerfer" <tsbogend@alpha.franken.de>,
"James E.J. Bottomley" <James.Bottomley@hansenpartnership.com>,
"Helge Deller" <deller@gmx.de>,
"Michael Ellerman" <mpe@ellerman.id.au>,
"Benjamin Herrenschmidt" <benh@kernel.crashing.org>,
"Paul Mackerras" <paulus@samba.org>,
"Heiko Carstens" <hca@linux.ibm.com>,
"Vasily Gorbik" <gor@linux.ibm.com>,
"Christian Borntraeger" <borntraeger@de.ibm.com>,
"Yoshinori Sato" <ysato@users.sourceforge.jp>,
"Rich Felker" <dalias@libc.org>,
"David S. Miller" <davem@davemloft.net>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Ingo Molnar" <mingo@redhat.com>,
"Borislav Petkov" <bp@alien8.de>, x86 <x86@kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>,
"Juri Lelli" <juri.lelli@redhat.com>,
"Vincent Guittot" <vincent.guittot@linaro.org>,
"Dietmar Eggemann" <dietmar.eggemann@arm.com>,
"Steven Rostedt" <rostedt@goodmis.org>,
"Ben Segall" <bsegall@google.com>, "Mel Gorman" <mgorman@suse.de>,
"Daniel Bristot de Oliveira" <bristot@redhat.com>,
"Arnd Bergmann" <arnd@arndb.de>,
"Linus Walleij" <linus.walleij@linaro.org>,
"Geert Uytterhoeven" <geert+renesas@glider.be>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Anshuman Khandual" <anshuman.khandual@arm.com>,
"Mike Rapoport" <rppt@kernel.org>,
"Mark Rutland" <mark.rutland@arm.com>,
"Ard Biesheuvel" <ardb@kernel.org>,
"YiFei Zhu" <yifeifz2@illinois.edu>,
"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
"Kefeng Wang" <wangkefeng.wang@huawei.com>,
"Sergei Trofimovich" <slyfox@gentoo.org>,
"David Hildenbrand" <david@redhat.com>,
"Randy Dunlap" <rdunlap@infradead.org>,
"Masahiro Yamada" <masahiroy@kernel.org>,
"Kees Cook" <keescook@chromium.org>,
"Nathan Chancellor" <nathan@kernel.org>,
"Nick Desaulniers" <ndesaulniers@google.com>,
"Chris Down" <chris@chrisdown.name>,
"Vipin Sharma" <vipinsh@google.com>,
"Rasmus Villemoes" <linux@rasmusvillemoes.dk>,
"Daniel Borkmann" <daniel@iogearbox.net>,
"Vlastimil Babka" <vbabka@suse.cz>,
"Frederic Weisbecker" <frederic@kernel.org>,
"Hugh Dickins" <hughd@google.com>,
"Michal Hocko" <mhocko@kernel.org>
Subject: Re: [PATCH 2/2] sched: Centralize SCHED_{SMT, MC, CLUSTER} definitions
Date: Fri, 15 Oct 2021 13:04:50 +0000 [thread overview]
Message-ID: <YWl8cogsS2Lah1mk@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <87bl3zlex8.mognet@arm.com>
On Fri, Oct 08, 2021 at 04:22:27PM +0100, Valentin Schneider wrote:
> So x86 has it default yes, and a lot of others (e.g. arm64) have it default
> no.
>
> IMO you don't gain much by disabling them. SCHED_MC and SCHED_CLUSTER only
> control the presence of a sched_domain_topology_level - if it's useless it
> gets degenerated at domain build time. Some valid reasons for not using
> them is if the architecture defines its own topology table (e.g. powerpc
> has CACHE and MC levels which are not gated behind any CONFIG).
>
> SCHED_SMT has an impact on code generated in sched/core.c, but that is also
> gated by a static key.
>
> So I'd say having them default yes is sensible. I'd even say we should
> change the "If unsure say N here." to "Y".
Right, so I tend to agree (and also that we should fix that Kconfig help
text). But it would be very nice to have feedback from the affected arch
maintainers.
WARNING: multiple messages have this Message-ID (diff)
From: Peter Zijlstra <peterz@infradead.org>
To: Valentin Schneider <valentin.schneider@arm.com>
Cc: "Barry Song" <21cnbao@gmail.com>,
LKML <linux-kernel@vger.kernel.org>,
LAK <linux-arm-kernel@lists.infradead.org>,
linux-ia64@vger.kernel.org, linux-mips@vger.kernel.org,
linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
linux-s390@vger.kernel.org, linux-sh@vger.kernel.org,
sparclinux@vger.kernel.org,
"Aubrey Li" <aubrey.li@linux.intel.com>,
"Barry Song" <song.bao.hua@hisilicon.com>,
"Tim Chen" <tim.c.chen@linux.intel.com>,
"Jonathan Cameron" <jonathan.cameron@huawei.com>,
"Russell King" <linux@armlinux.org.uk>,
"Catalin Marinas" <catalin.marinas@arm.com>,
"Will Deacon" <will@kernel.org>,
"Thomas Bogendoerfer" <tsbogend@alpha.franken.de>,
"James E.J. Bottomley" <James.Bottomley@hansenpartnership.com>,
"Helge Deller" <deller@gmx.de>,
"Michael Ellerman" <mpe@ellerman.id.au>,
"Benjamin Herrenschmidt" <benh@kernel.crashing.org>,
"Paul Mackerras" <paulus@samba.org>,
"Heiko Carstens" <hca@linux.ibm.com>,
"Vasily Gorbik" <gor@linux.ibm.com>,
"Christian Borntraeger" <borntraeger@de.ibm.com>,
"Yoshinori Sato" <ysato@users.sourceforge.jp>,
"Rich Felker" <dalias@libc.org>,
"David S. Miller" <davem@davemloft.net>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Ingo Molnar" <mingo@redhat.com>,
"Borislav Petkov" <bp@alien8.de>, x86 <x86@kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>,
"Juri Lelli" <juri.lelli@redhat.com>,
"Vincent Guittot" <vincent.guittot@linaro.org>,
"Dietmar Eggemann" <dietmar.eggemann@arm.com>,
"Steven Rostedt" <rostedt@goodmis.org>,
"Ben Segall" <bsegall@google.com>, "Mel Gorman" <mgorman@suse.de>,
"Daniel Bristot de Oliveira" <bristot@redhat.com>,
"Arnd Bergmann" <arnd@arndb.de>,
"Linus Walleij" <linus.walleij@linaro.org>,
"Geert Uytterhoeven" <geert+renesas@glider.be>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Anshuman Khandual" <anshuman.khandual@arm.com>,
"Mike Rapoport" <rppt@kernel.org>,
"Mark Rutland" <mark.rutland@arm.com>,
"Ard Biesheuvel" <ardb@kernel.org>,
"YiFei Zhu" <yifeifz2@illinois.edu>,
"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
"Kefeng Wang" <wangkefeng.wang@huawei.com>,
"Sergei Trofimovich" <slyfox@gentoo.org>,
"David Hildenbrand" <david@redhat.com>,
"Randy Dunlap" <rdunlap@infradead.org>,
"Masahiro Yamada" <masahiroy@kernel.org>,
"Kees Cook" <keescook@chromium.org>,
"Nathan Chancellor" <nathan@kernel.org>,
"Nick Desaulniers" <ndesaulniers@google.com>,
"Chris Down" <chris@chrisdown.name>,
"Vipin Sharma" <vipinsh@google.com>,
"Rasmus Villemoes" <linux@rasmusvillemoes.dk>,
"Daniel Borkmann" <daniel@iogearbox.net>,
"Vlastimil Babka" <vbabka@suse.cz>,
"Frederic Weisbecker" <frederic@kernel.org>,
"Hugh Dickins" <hughd@google.com>,
"Michal Hocko" <mhocko@kernel.org>
Subject: Re: [PATCH 2/2] sched: Centralize SCHED_{SMT, MC, CLUSTER} definitions
Date: Fri, 15 Oct 2021 15:04:50 +0200 [thread overview]
Message-ID: <YWl8cogsS2Lah1mk@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <87bl3zlex8.mognet@arm.com>
On Fri, Oct 08, 2021 at 04:22:27PM +0100, Valentin Schneider wrote:
> So x86 has it default yes, and a lot of others (e.g. arm64) have it default
> no.
>
> IMO you don't gain much by disabling them. SCHED_MC and SCHED_CLUSTER only
> control the presence of a sched_domain_topology_level - if it's useless it
> gets degenerated at domain build time. Some valid reasons for not using
> them is if the architecture defines its own topology table (e.g. powerpc
> has CACHE and MC levels which are not gated behind any CONFIG).
>
> SCHED_SMT has an impact on code generated in sched/core.c, but that is also
> gated by a static key.
>
> So I'd say having them default yes is sensible. I'd even say we should
> change the "If unsure say N here." to "Y".
Right, so I tend to agree (and also that we should fix that Kconfig help
text). But it would be very nice to have feedback from the affected arch
maintainers.
WARNING: multiple messages have this Message-ID (diff)
From: Peter Zijlstra <peterz@infradead.org>
To: Valentin Schneider <valentin.schneider@arm.com>
Cc: "Juri Lelli" <juri.lelli@redhat.com>,
"Mark Rutland" <mark.rutland@arm.com>,
"Kefeng Wang" <wangkefeng.wang@huawei.com>,
"Rich Felker" <dalias@libc.org>,
linux-ia64@vger.kernel.org,
"Geert Uytterhoeven" <geert+renesas@glider.be>,
linux-sh@vger.kernel.org,
"Catalin Marinas" <catalin.marinas@arm.com>,
"Linus Walleij" <linus.walleij@linaro.org>,
"David Hildenbrand" <david@redhat.com>, x86 <x86@kernel.org>,
linux-mips@vger.kernel.org,
"James E.J. Bottomley" <James.Bottomley@hansenpartnership.com>,
"Hugh Dickins" <hughd@google.com>,
"Paul Mackerras" <paulus@samba.org>,
"H. Peter Anvin" <hpa@zytor.com>,
sparclinux@vger.kernel.org, "Will Deacon" <will@kernel.org>,
"Ard Biesheuvel" <ardb@kernel.org>,
linux-s390@vger.kernel.org,
"Vincent Guittot" <vincent.guittot@linaro.org>,
"Arnd Bergmann" <arnd@arndb.de>,
"Yoshinori Sato" <ysato@users.sourceforge.jp>,
"YiFei Zhu" <yifeifz2@illinois.edu>,
"Helge Deller" <deller@gmx.de>,
"Aubrey Li" <aubrey.li@linux.intel.com>,
"Barry Song" <21cnbao@gmail.com>,
"Russell King" <linux@armlinux.org.uk>,
"Christian Borntraeger" <borntraeger@de.ibm.com>,
"Ingo Molnar" <mingo@redhat.com>, "Mel Gorman" <mgorman@suse.de>,
"Masahiro Yamada" <masahiroy@kernel.org>,
"Frederic Weisbecker" <frederic@kernel.org>,
"Kees Cook" <keescook@chromium.org>,
"Vasily Gorbik" <gor@linux.ibm.com>,
"Anshuman Khandual" <anshuman.khandual@arm.com>,
"Vlastimil Babka" <vbabka@suse.cz>,
"Vipin Sharma" <vipinsh@google.com>,
"Heiko Carstens" <hca@linux.ibm.com>,
"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
"Steven Rostedt" <rostedt@goodmis.org>,
"Nathan Chancellor" <nathan@kernel.org>,
"Borislav Petkov" <bp@alien8.de>,
"Sergei Trofimovich" <slyfox@gentoo.org>,
"Jonathan Cameron" <jonathan.cameron@huawei.com>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Michal Hocko" <mhocko@kernel.org>,
"Dietmar Eggemann" <dietmar.eggemann@arm.com>,
LAK <linux-arm-kernel@lists.infradead.org>,
"Barry Song" <song.bao.hua@hisilicon.com>,
"Ben Segall" <bsegall@google.com>,
"Thomas Bogendoerfer" <tsbogend@alpha.franken.de>,
"Daniel Borkmann" <daniel@iogearbox.net>,
linux-parisc@vger.kernel.org, "Chris Down" <chris@chrisdown.name>,
linuxppc-dev@lists.ozlabs.org,
"Randy Dunlap" <rdunlap@infradead.org>,
"Nick Desaulniers" <ndesaulniers@google.com>,
LKML <linux-kernel@vger.kernel.org>,
"Rasmus Villemoes" <linux@rasmusvillemoes.dk>,
"Daniel Bristot de Oliveira" <bristot@redhat.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Tim Chen" <tim.c.chen@linux.intel.com>,
"David S. Miller" <davem@davemloft.net>,
"Mike Rapoport" <rppt@kernel.org>
Subject: Re: [PATCH 2/2] sched: Centralize SCHED_{SMT, MC, CLUSTER} definitions
Date: Fri, 15 Oct 2021 15:04:50 +0200 [thread overview]
Message-ID: <YWl8cogsS2Lah1mk@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <87bl3zlex8.mognet@arm.com>
On Fri, Oct 08, 2021 at 04:22:27PM +0100, Valentin Schneider wrote:
> So x86 has it default yes, and a lot of others (e.g. arm64) have it default
> no.
>
> IMO you don't gain much by disabling them. SCHED_MC and SCHED_CLUSTER only
> control the presence of a sched_domain_topology_level - if it's useless it
> gets degenerated at domain build time. Some valid reasons for not using
> them is if the architecture defines its own topology table (e.g. powerpc
> has CACHE and MC levels which are not gated behind any CONFIG).
>
> SCHED_SMT has an impact on code generated in sched/core.c, but that is also
> gated by a static key.
>
> So I'd say having them default yes is sensible. I'd even say we should
> change the "If unsure say N here." to "Y".
Right, so I tend to agree (and also that we should fix that Kconfig help
text). But it would be very nice to have feedback from the affected arch
maintainers.
next prev parent reply other threads:[~2021-10-15 13:04 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-08 11:53 [PATCH 0/2] sched: cleanup CONFIG_SCHED_MC & friends Valentin Schneider
2021-10-08 11:53 ` Valentin Schneider
2021-10-08 11:53 ` Valentin Schneider
2021-10-08 11:53 ` [PATCH 1/2] sched: Move Kconfig.preempt to sched/Kconfig Valentin Schneider
2021-10-08 11:53 ` Valentin Schneider
2021-10-08 11:53 ` Valentin Schneider
2021-10-08 11:53 ` [PATCH 2/2] sched: Centralize SCHED_{SMT, MC, CLUSTER} definitions Valentin Schneider
2021-10-08 11:53 ` Valentin Schneider
2021-10-08 11:53 ` Valentin Schneider
2021-10-08 12:37 ` Barry Song
2021-10-08 12:37 ` Barry Song
2021-10-08 12:37 ` Barry Song
2021-10-08 15:22 ` Valentin Schneider
2021-10-08 15:22 ` Valentin Schneider
2021-10-08 15:22 ` Valentin Schneider
2021-10-15 13:04 ` Peter Zijlstra [this message]
2021-10-15 13:04 ` Peter Zijlstra
2021-10-15 13:04 ` Peter Zijlstra
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