From 1ca86fafc532c9d6bc722aa49a8a0c35eb117f05 Mon Sep 17 00:00:00 2001 From: Laurent Dufour Date: Tue, 17 Apr 2018 16:33:07 +0200 Subject: [PATCH] FROMLIST: mm: introduce CONFIG_SPECULATIVE_PAGE_FAULT This configuration variable will be used to build the code needed to handle speculative page fault. By default it is turned off, and activated depending on architecture support, SMP and MMU. Suggested-by: Thomas Gleixner Suggested-by: David Rientjes Signed-off-by: Laurent Dufour Change-Id: I17123124ec0667a0f0af741a740e5219d278620c Link: https://lore.kernel.org/lkml/1523975611-15978-2-git-send-email-ldufour@linux.vnet.ibm.com/ Bug: 161210518 Signed-off-by: Vinayak Menon --- mm/Kconfig | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/mm/Kconfig b/mm/Kconfig index 390165ffbb0f..b032314de131 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -821,6 +821,28 @@ config PERCPU_STATS information includes global and per chunk statistics, which can be used to help understand percpu memory usage. +config ARCH_SUPPORTS_SPECULATIVE_PAGE_FAULT + def_bool n + +config SPECULATIVE_PAGE_FAULT + bool "Speculative page faults" + default y + depends on ARCH_SUPPORTS_SPECULATIVE_PAGE_FAULT + depends on MMU && SMP + help + Try to handle user space page faults without holding the mmap_sem. + + This should allow better concurrency for massively threaded process + since the page fault handler will not wait for other threads memory + layout change to be done, assuming that this change is done in another + part of the process's memory space. This type of page fault is named + speculative page fault. + + If the speculative page fault fails because of a concurrency is + detected or because underlying PMD or PTE tables are not yet + allocating, it is failing its processing and a classic page fault + is then tried. + config GUP_BENCHMARK bool "Enable infrastructure for get_user_pages() and related calls benchmarking" help