linux-kernel - [PATCH v2 0/2] send tlb_remove_table_smp

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Date:   Tue, 20 Jun 2023 17:46:16 +0300
From:   Yair Podemsky <ypodemsk@...hat.com>
To:     mtosatti@...hat.com, ppandit@...hat.com, david@...hat.com,
        linux@...linux.org.uk, mpe@...erman.id.au, npiggin@...il.com,
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        sparclinux@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc:     ypodemsk@...hat.com
Subject: [PATCH v2 0/2] send tlb_remove_table_smp_sync IPI only to necessary CPUs

Currently the tlb_remove_table_smp_sync IPI is sent to all CPUs
indiscriminately, this causes unnecessary work and delays notable in
real-time use-cases and isolated cpus.
By limiting the IPI to only be sent to cpus referencing the effected
mm.
a config to differentiate architectures that support mm_cpumask from
those that don't will allow safe usage of this feature.

changes from -v1:
- Previous version included a patch to only send the IPI to CPU's with
context_tracking in the kernel space, this was removed due to race 
condition concerns.
- for archs that do not maintain mm_cpumask the mask used should be
 cpu_online_mask (Peter Zijlstra).
 
 v1: https://lore.kernel.org/all/20230404134224.137038-1-ypodemsk@redhat.com/

Yair Podemsky (2):
  arch: Introduce ARCH_HAS_CPUMASK_BITS
  mm/mmu_gather: send tlb_remove_table_smp_sync IPI only to MM CPUs

 arch/Kconfig              |  8 ++++++++
 arch/arm/Kconfig          |  1 +
 arch/powerpc/Kconfig      |  1 +
 arch/s390/Kconfig         |  1 +
 arch/sparc/Kconfig        |  1 +
 arch/x86/Kconfig          |  1 +
 include/asm-generic/tlb.h |  4 ++--
 mm/khugepaged.c           |  4 ++--
 mm/mmu_gather.c           | 17 ++++++++++++-----
 9 files changed, 29 insertions(+), 9 deletions(-)

-- 
2.39.3