From: David Hildenbrand <david@redhat.com>
To: Kevin Brodsky <kevin.brodsky@arm.com>, linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org,
Alexander Gordeev <agordeev@linux.ibm.com>,
Andreas Larsson <andreas@gaisler.com>,
Andrew Morton <akpm@linux-foundation.org>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Borislav Petkov <bp@alien8.de>,
Catalin Marinas <catalin.marinas@arm.com>,
Christophe Leroy <christophe.leroy@csgroup.eu>,
Dave Hansen <dave.hansen@linux.intel.com>,
"David S. Miller" <davem@davemloft.net>,
"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
Jann Horn <jannh@google.com>, Juergen Gross <jgross@suse.com>,
"Liam R. Howlett" <Liam.Howlett@oracle.com>,
Lorenzo Stoakes <lorenzo.stoakes@oracle.com>,
Madhavan Srinivasan <maddy@linux.ibm.com>,
Michael Ellerman <mpe@ellerman.id.au>,
Michal Hocko <mhocko@suse.com>, Mike Rapoport <rppt@kernel.org>,
Nicholas Piggin <npiggin@gmail.com>,
Peter Zijlstra <peterz@infradead.org>,
Ryan Roberts <ryan.roberts@arm.com>,
Suren Baghdasaryan <surenb@google.com>,
Thomas Gleixner <tglx@linutronix.de>,
Vlastimil Babka <vbabka@suse.cz>, Will Deacon <will@kernel.org>,
Yeoreum Yun <yeoreum.yun@arm.com>,
linux-arm-kernel@lists.infradead.org,
linuxppc-dev@lists.ozlabs.org, sparclinux@vger.kernel.org,
xen-devel@lists.xenproject.org, x86@kernel.org
Subject: Re: [PATCH v3 13/13] mm: introduce arch_wants_lazy_mmu_mode()
Date: Thu, 23 Oct 2025 22:10:39 +0200 [thread overview]
Message-ID: <3d6bba2d-9739-41d0-8f3a-f8b11620c33f@redhat.com> (raw)
In-Reply-To: <20251015082727.2395128-14-kevin.brodsky@arm.com>
On 15.10.25 10:27, Kevin Brodsky wrote:
> powerpc decides at runtime whether the lazy MMU mode should be used.
>
> To avoid the overhead associated with managing
> task_struct::lazy_mmu_state if the mode isn't used, introduce
> arch_wants_lazy_mmu_mode() and bail out of lazy_mmu_mode_* if it
> returns false. Add a default definition returning true, and an
> appropriate implementation for powerpc.
>
> Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
> ---
> This patch seemed like a good idea to start with, but now I'm not so
> sure that the churn added to the generic layer is worth it.
Exactly my thoughts :)
I think we need evidence that this is really worth it for optimizing out
basically a counter update on powerpc.
--
Cheers
David / dhildenb
next prev parent reply other threads:[~2025-10-23 20:10 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-15 8:27 [PATCH v3 00/13] Nesting support for lazy MMU mode Kevin Brodsky
2025-10-15 8:27 ` [PATCH v3 01/13] powerpc/64s: Do not re-activate batched TLB flush Kevin Brodsky
2025-10-15 8:27 ` [PATCH v3 02/13] x86/xen: simplify flush_lazy_mmu() Kevin Brodsky
2025-10-15 16:52 ` Dave Hansen
2025-10-16 7:32 ` Kevin Brodsky
2025-10-15 8:27 ` [PATCH v3 03/13] powerpc/mm: implement arch_flush_lazy_mmu_mode() Kevin Brodsky
2025-10-23 19:36 ` David Hildenbrand
2025-10-24 12:09 ` Kevin Brodsky
2025-10-24 14:42 ` David Hildenbrand
2025-10-24 14:54 ` Kevin Brodsky
2025-10-15 8:27 ` [PATCH v3 04/13] sparc/mm: " Kevin Brodsky
2025-10-23 19:37 ` David Hildenbrand
2025-10-15 8:27 ` [PATCH v3 05/13] mm: introduce CONFIG_ARCH_LAZY_MMU Kevin Brodsky
2025-10-18 9:52 ` Mike Rapoport
2025-10-20 10:37 ` Kevin Brodsky
2025-10-23 19:38 ` David Hildenbrand
2025-10-15 8:27 ` [PATCH v3 06/13] mm: introduce generic lazy_mmu helpers Kevin Brodsky
2025-10-17 15:54 ` Alexander Gordeev
2025-10-20 10:32 ` Kevin Brodsky
2025-10-23 19:52 ` David Hildenbrand
2025-10-24 12:13 ` Kevin Brodsky
2025-10-24 13:27 ` David Hildenbrand
2025-10-24 14:32 ` Kevin Brodsky
2025-10-27 16:24 ` David Hildenbrand
2025-10-28 10:34 ` Kevin Brodsky
2025-10-15 8:27 ` [PATCH v3 07/13] mm: enable lazy_mmu sections to nest Kevin Brodsky
2025-10-23 20:00 ` David Hildenbrand
2025-10-24 12:16 ` Kevin Brodsky
2025-10-24 13:23 ` David Hildenbrand
2025-10-24 14:33 ` Kevin Brodsky
2025-10-15 8:27 ` [PATCH v3 08/13] arm64: mm: replace TIF_LAZY_MMU with in_lazy_mmu_mode() Kevin Brodsky
2025-10-15 8:27 ` [PATCH v3 09/13] powerpc/mm: replace batch->active " Kevin Brodsky
2025-10-23 20:02 ` David Hildenbrand
2025-10-24 12:16 ` Kevin Brodsky
2025-10-15 8:27 ` [PATCH v3 10/13] sparc/mm: " Kevin Brodsky
2025-10-23 20:03 ` David Hildenbrand
2025-10-15 8:27 ` [PATCH v3 11/13] x86/xen: use lazy_mmu_state when context-switching Kevin Brodsky
2025-10-23 20:06 ` David Hildenbrand
2025-10-24 14:47 ` David Woodhouse
2025-10-24 14:51 ` David Hildenbrand
2025-10-24 15:13 ` David Woodhouse
2025-10-24 15:16 ` David Hildenbrand
2025-10-24 15:38 ` John Paul Adrian Glaubitz
2025-10-24 15:47 ` David Hildenbrand
2025-10-24 15:51 ` John Paul Adrian Glaubitz
2025-10-27 12:38 ` David Hildenbrand
2025-10-24 22:52 ` Demi Marie Obenour
2025-10-27 12:29 ` David Hildenbrand
2025-10-27 13:32 ` Kevin Brodsky
2025-10-24 15:05 ` Kevin Brodsky
2025-10-24 15:17 ` David Woodhouse
2025-10-27 13:38 ` Kevin Brodsky
2025-10-15 8:27 ` [PATCH v3 12/13] mm: bail out of lazy_mmu_mode_* in interrupt context Kevin Brodsky
2025-10-23 20:08 ` David Hildenbrand
2025-10-24 12:17 ` Kevin Brodsky
2025-10-15 8:27 ` [PATCH v3 13/13] mm: introduce arch_wants_lazy_mmu_mode() Kevin Brodsky
2025-10-23 20:10 ` David Hildenbrand [this message]
2025-10-24 12:17 ` Kevin Brodsky
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