linux-kernel - [RFC v2 10/10] mm: Introduce CONFIG_MEM_RANGE

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Date:   Wed, 24 May 2017 13:20:01 +0200
From:   Laurent Dufour <ldufour@...ux.vnet.ibm.com>
To:     linux-mm@...ck.org
Cc:     Davidlohr Bueso <dave@...olabs.net>, akpm@...ux-foundation.org,
        Jan Kara <jack@...e.cz>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Michal Hocko <mhocko@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Andi Kleen <andi@...stfloor.org>, haren@...ux.vnet.ibm.com,
        aneesh.kumar@...ux.vnet.ibm.com, khandual@...ux.vnet.ibm.com,
        paulmck@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org
Subject: [RFC v2 10/10] mm: Introduce CONFIG_MEM_RANGE_LOCK

A new configuration variable is introduced to activate the use of
range lock instead of semaphore to protect per process memory layout.

This range lock is replacing the use of a semaphore for mmap_sem.

Currently only available for X86_64 and PPC64 architectures.

By default this option is turned off and requires the EXPERT mode
since it is not yet complete.

Signed-off-by: Laurent Dufour <ldufour@...ux.vnet.ibm.com>
---
 mm/Kconfig | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/mm/Kconfig b/mm/Kconfig
index beb7a455915d..955d9a735a49 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -309,6 +309,18 @@ config NEED_BOUNCE_POOL
 	bool
 	default y if TILE && USB_OHCI_HCD
 
+config MEM_RANGE_LOCK
+	bool "Use range lock for process's memory layout"
+	default n
+	depends on EXPERT
+	depends on MMU
+	depends on X86_64 || PPC64
+	help
+	  Use range lock instead of traditional semaphore to protect per
+	  process memory layout. This is required when dealing with massive
+	  threaded process on very large system (more than 80 cpu threads).
+	  If unsure say n.
+
 config NR_QUICK
 	int
 	depends on QUICKLIST
-- 
2.7.4