linux-kernel - Re: [PATCH v8 2/3] mm: replace hardcoded 3% with admin_reserve

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Date:	Mon, 8 Apr 2013 12:39:11 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Andrew Shewmaker <agshew@...il.com>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	alan@...rguk.ukuu.org.uk, simon.jeons@...il.com,
	ric.masonn@...il.com
Subject: Re: [PATCH v8 2/3] mm: replace hardcoded 3% with
 admin_reserve_pages knob

On Mon, 8 Apr 2013 15:05:10 -0400 Andrew Shewmaker <agshew@...il.com> wrote:

> Add an admin_reserve_kbytes knob to allow admins to change the
> hardcoded memory reserve to something other than 3%, which
> may be multiple gigabytes on large memory systems. Only about
> 8MB is necessary to enable recovery in the default mode, and
> only a few hundred MB are required even when overcommit is
> disabled.

And the only change that v8 made was to revert earlier fixes, so I'll
skip this version as well.

--- a/include/linux/mm.h~mm-replace-hardcoded-3%-with-admin_reserve_pages-knob-v8
+++ a/include/linux/mm.h
@@ -45,7 +45,6 @@ extern int sysctl_legacy_va_layout;
 #include <asm/processor.h>
 
 extern unsigned long sysctl_user_reserve_kbytes;
-extern unsigned long sysctl_admin_reserve_kbytes;
 
 #define nth_page(page,n) pfn_to_page(page_to_pfn((page)) + (n))
 
--- a/kernel/sysctl.c~mm-replace-hardcoded-3%-with-admin_reserve_pages-knob-v8
+++ a/kernel/sysctl.c
@@ -97,6 +97,7 @@
 /* External variables not in a header file. */
 extern int sysctl_overcommit_memory;
 extern int sysctl_overcommit_ratio;
+extern unsigned long sysctl_admin_reserve_kbytes;
 extern int max_threads;
 extern int suid_dumpable;
 #ifdef CONFIG_COREDUMP
--- a/mm/mmap.c~mm-replace-hardcoded-3%-with-admin_reserve_pages-knob-v8
+++ a/mm/mmap.c
@@ -168,7 +168,7 @@ int __vm_enough_memory(struct mm_struct
 		 * Reserve some for root
 		 */
 		if (!cap_sys_admin)
-			free -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10);
+			free -= sysctl_admin_reserve_kbytes  >> (PAGE_SHIFT - 10);
 
 		if (free > pages)
 			return 0;
--- a/mm/nommu.c~mm-replace-hardcoded-3%-with-admin_reserve_pages-knob-v8
+++ a/mm/nommu.c
@@ -1932,7 +1932,7 @@ int __vm_enough_memory(struct mm_struct
 		 * Reserve some for root
 		 */
 		if (!cap_sys_admin)
-			free -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10);
+			free -= sysctl_admin_reserve_kbytes  >> (PAGE_SHIFT - 10);
 
 		if (free > pages)
 			return 0;
_

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