Re: [PATCH v2 3/5] lazy tlb: shoot lazies, a non-refcounting lazy tlb option
From: Randy Dunlap <hidden>
Date: 2020-12-14 07:06:22
Also in:
linux-arch, linux-mm, lkml
On 12/13/20 10:53 PM, Nicholas Piggin wrote:
quoted hunk ↗ jump to hunk
diff --git a/arch/Kconfig b/arch/Kconfig index 84faaba66364..e69c974369cc 100644 --- a/arch/Kconfig +++ b/arch/Kconfig@@ -443,9 +443,22 @@ config MMU_LAZY_TLB config MMU_LAZY_TLB_REFCOUNT def_bool y depends on MMU_LAZY_TLB + depends on !MMU_LAZY_TLB_SHOOTDOWN help - This must be enabled if MMU_LAZY_TLB is enabled until the next - patch. + This refcounts the mm that is used as the lazy TLB mm when switching + switching to a kernel thread.
duplicate "switching".
+ +config MMU_LAZY_TLB_SHOOTDOWN + bool + depends on MMU_LAZY_TLB + help + Instead of refcounting the "lazy tlb" mm struct, which can cause + contention with multi-threaded apps on large multiprocessor systems, + this option causes __mmdrop to IPI all CPUs in the mm_cpumask and + switch to init_mm if they were using the to-be-freed mm as the lazy + tlb. To implement this, architectures must use _lazy_tlb variants of + mm refcounting, and mm_cpumask must include at least all possible + CPUs in which mm might be lazy. config ARCH_HAVE_NMI_SAFE_CMPXCHG bool
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