From: Pasha Tatashin <pasha.tatashin@soleen•com>
To: Andrew Morton <akpm@linux-foundation•org>
Cc: Lance Yang <lance.yang@linux•dev>,
peterz@infradead•org, david@kernel•org, dave.hansen@intel•com,
dave.hansen@linux•intel.com, ypodemsk@redhat•com,
hughd@google•com, will@kernel•org, aneesh.kumar@kernel•org,
npiggin@gmail•com, tglx@linutronix•de, mingo@redhat•com,
bp@alien8•de, x86@kernel•org, hpa@zytor•com, arnd@arndb•de,
ljs@kernel•org, ziy@nvidia•com, baolin.wang@linux•alibaba.com,
Liam.Howlett@oracle•com, npache@redhat•com, ryan.roberts@arm•com,
dev.jain@arm•com, baohua@kernel•org, shy828301@gmail•com,
riel@surriel•com, jannh@google•com, jgross@suse•com,
seanjc@google•com, pbonzini@redhat•com,
boris.ostrovsky@oracle•com, virtualization@lists•linux.dev,
kvm@vger•kernel.org, linux-arch@vger•kernel.org,
linux-mm@kvack•org, linux-kernel@vger•kernel.org,
ioworker0@gmail•com, roman.gushchin@linux•dev
Subject: Re: [PATCH 7.2 v10 0/2] skip redundant sync IPIs when TLB flush sent them
Date: Fri, 24 Apr 2026 13:37:04 +0000 [thread overview]
Message-ID: <aetw4aoABYj3keMh@plex> (raw)
In-Reply-To: <20260424063024.ce42ee6a5546e4d9337dd007@linux-foundation.org>
On 04-24 06:30, Andrew Morton wrote:
> On Fri, 24 Apr 2026 14:25:26 +0800 Lance Yang <lance.yang@linux•dev> wrote:
>
> > When page table operations require synchronization with software/lockless
> > walkers, they call tlb_remove_table_sync_{one,rcu}() after flushing the
> > TLB (tlb->freed_tables or tlb->unshared_tables).
> >
> > On architectures where the TLB flush already sends IPIs to all target CPUs,
> > the subsequent sync IPI broadcast is redundant. This is not only costly on
> > large systems where it disrupts all CPUs even for single-process page table
> > operations, but has also been reported to hurt RT workloads[1].
> >
> > This series introduces tlb_table_flush_implies_ipi_broadcast() to check if
> > the prior TLB flush already provided the necessary synchronization. When
> > true, the sync calls can early-return.
> >
> > A few cases rely on this synchronization:
> >
> > 1) hugetlb PMD unshare[2]: The problem is not the freeing but the reuse
> > of the PMD table for other purposes in the last remaining user after
> > unsharing.
> >
> > 2) khugepaged collapse[3]: Ensure no concurrent GUP-fast before collapsing
> > and (possibly) freeing the page table / re-depositing it.
>
> Sashiko questions:
> https://sashiko.dev/#/patchset/20260424062528.71951-1-lance.yang@linux.dev
>
> (I never know if my Sashiko emails are welcome/useful. Maybe Sashiko
> said the same stuff about v9 and it's all wrong. But better safe than
> sorry!)
These emails are helpful; but, I do not believe you should have to
manually follow up with a link to every new patch series.
Perhaps Sashiko could automatically send a summary email in response to
the cover letter, or provide a link once the reviews are complete. For
the kexec ML, we opted-in with Roman to receive automated emails from
sashiko.
+Cc: Roman.
>
>
next prev parent reply other threads:[~2026-04-24 13:37 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-24 6:25 [PATCH 7.2 v10 0/2] skip redundant sync IPIs when TLB flush sent them Lance Yang
2026-04-24 6:25 ` [PATCH 7.2 v10 1/2] mm/mmu_gather: prepare to skip redundant sync IPIs Lance Yang
2026-04-24 15:04 ` Peter Zijlstra
2026-04-24 15:52 ` Dave Hansen
2026-05-27 1:44 ` Andrew Morton
2026-04-24 15:40 ` Lance Yang
2026-04-24 6:25 ` [PATCH 7.2 v10 2/2] x86/tlb: skip redundant sync IPIs for native TLB flush Lance Yang
2026-04-24 15:12 ` Peter Zijlstra
2026-04-24 15:49 ` Lance Yang
2026-04-24 13:30 ` [PATCH 7.2 v10 0/2] skip redundant sync IPIs when TLB flush sent them Andrew Morton
2026-04-24 13:37 ` Pasha Tatashin [this message]
2026-04-24 14:15 ` Andrew Morton
2026-04-24 14:20 ` David Hildenbrand (Arm)
2026-04-24 14:31 ` Andrew Morton
2026-04-24 14:40 ` Pasha Tatashin
2026-04-24 18:36 ` David Hildenbrand (Arm)
2026-04-24 18:50 ` Yosry Ahmed
2026-04-24 19:01 ` Peter Zijlstra
2026-04-24 19:12 ` Zi Yan
2026-04-24 19:15 ` Yosry Ahmed
2026-04-25 0:58 ` SeongJae Park
2026-04-24 19:22 ` Peter Zijlstra
2026-04-24 19:35 ` Peter Zijlstra
2026-04-24 20:03 ` Roman Gushchin
2026-04-24 20:11 ` Peter Zijlstra
2026-05-29 11:10 ` Peter Zijlstra
2026-04-24 19:08 ` Andrew Morton
2026-04-24 19:09 ` David Hildenbrand (Arm)
2026-04-24 19:17 ` Peter Zijlstra
2026-04-24 19:24 ` David Hildenbrand (Arm)
2026-04-24 19:18 ` Yosry Ahmed
2026-04-25 1:12 ` SeongJae Park
2026-04-25 5:17 ` David Hildenbrand (Arm)
2026-04-25 11:36 ` Andrew Morton
2026-04-27 8:53 ` David Hildenbrand (Arm)
2026-04-25 1:19 ` SeongJae Park
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