The patch titled
Subject: mm: replace hardcoded 3% with admin_reserve_pages knob
has been removed from the -mm tree. Its filename was
mm-replace-hardcoded-3%-with-admin_reserve_pages-knob.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: Andrew Shewmaker <agshew@xxxxxxxxx>
Subject: mm: replace hardcoded 3% with admin_reserve_pages knob
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.
This affects OVERCOMMIT_GUESS and OVERCOMMIT_NEVER.
admin_reserve_kbytes is initialized to min(3% free pages, 8MB)
I arrived at 8MB by summing the RSS of sshd or login,
bash, and top.
Please see first patch in this series for full background,
motivation, testing, and full changelog.
[akpm@xxxxxxxxxxxxxxxxxxxx: coding-style fixes]
[akpm@xxxxxxxxxxxxxxxxxxxx: make init_admin_reserve() static]
Signed-off-by: Andrew Shewmaker <agshew@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/sysctl/vm.txt | 30 ++++++++++++++++++++++++++++++
include/linux/mm.h | 1 +
kernel/sysctl.c | 7 +++++++
mm/mmap.c | 30 ++++++++++++++++++++++++++----
mm/nommu.c | 30 ++++++++++++++++++++++++++----
5 files changed, 90 insertions(+), 8 deletions(-)
diff -puN Documentation/sysctl/vm.txt~mm-replace-hardcoded-3%-with-admin_reserve_pages-knob Documentation/sysctl/vm.txt
--- a/Documentation/sysctl/vm.txt~mm-replace-hardcoded-3%-with-admin_reserve_pages-knob
+++ a/Documentation/sysctl/vm.txt
@@ -18,6 +18,7 @@ files can be found in mm/swap.c.
Currently, these files are in /proc/sys/vm:
+- admin_reserve_kbytes
- block_dump
- compact_memory
- dirty_background_bytes
@@ -59,6 +60,35 @@ Currently, these files are in /proc/sys/
==============================================================
+admin_reserve_kbytes
+
+The amount of free memory in the system that should be reserved for users
+with the capability cap_sys_admin.
+
+admin_reserve_kbytes defaults to min(3% of free pages, 8MB)
+
+That should provide enough for the admin to log in and kill a process,
+if necessary, under the default overcommit 'guess' mode.
+
+Systems running under overcommit 'never' should increase this to account
+for the full Virtual Memory Size of programs used to recover. Otherwise,
+root may not be able to log in to recover the system.
+
+How do you calculate a minimum useful reserve?
+
+sshd or login + bash (or some other shell) + top (or ps, kill, etc.)
+
+For overcommit 'guess', we can sum resident set sizes (RSS).
+On x86_64 this is about 8MB.
+
+For overcommit 'never', we can take the max of their virtual sizes (VSZ)
+and add the sum of their RSS.
+On x86_64 this is about 128MB.
+
+Changing this takes effect whenever an application requests memory.
+
+==============================================================
+
block_dump
block_dump enables block I/O debugging when set to a nonzero value. More
diff -puN include/linux/mm.h~mm-replace-hardcoded-3%-with-admin_reserve_pages-knob include/linux/mm.h
--- a/include/linux/mm.h~mm-replace-hardcoded-3%-with-admin_reserve_pages-knob
+++ a/include/linux/mm.h
@@ -45,6 +45,7 @@ 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))
diff -puN kernel/sysctl.c~mm-replace-hardcoded-3%-with-admin_reserve_pages-knob kernel/sysctl.c
--- a/kernel/sysctl.c~mm-replace-hardcoded-3%-with-admin_reserve_pages-knob
+++ a/kernel/sysctl.c
@@ -1436,6 +1436,13 @@ static struct ctl_table vm_table[] = {
.mode = 0644,
.proc_handler = proc_doulongvec_minmax,
},
+ {
+ .procname = "admin_reserve_kbytes",
+ .data = &sysctl_admin_reserve_kbytes,
+ .maxlen = sizeof(sysctl_admin_reserve_kbytes),
+ .mode = 0644,
+ .proc_handler = proc_doulongvec_minmax,
+ },
{ }
};
diff -puN mm/mmap.c~mm-replace-hardcoded-3%-with-admin_reserve_pages-knob mm/mmap.c
--- a/mm/mmap.c~mm-replace-hardcoded-3%-with-admin_reserve_pages-knob
+++ a/mm/mmap.c
@@ -85,6 +85,7 @@ int sysctl_overcommit_memory __read_most
int sysctl_overcommit_ratio __read_mostly = 50; /* default is 50% */
int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT;
unsigned long sysctl_user_reserve_kbytes __read_mostly = 1UL << 17; /* 128MB */
+unsigned long sysctl_admin_reserve_kbytes __read_mostly = 1UL << 13; /* 8MB */
/*
* Make sure vm_committed_as in one cacheline and not cacheline shared with
* other variables. It can be updated by several CPUs frequently.
@@ -164,10 +165,10 @@ int __vm_enough_memory(struct mm_struct
free -= totalreserve_pages;
/*
- * Leave the last 3% for root
+ * Reserve some for root
*/
if (!cap_sys_admin)
- free -= free / 32;
+ free -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10);
if (free > pages)
return 0;
@@ -178,10 +179,10 @@ int __vm_enough_memory(struct mm_struct
allowed = (totalram_pages - hugetlb_total_pages())
* sysctl_overcommit_ratio / 100;
/*
- * Leave the last 3% for root
+ * Reserve some for root
*/
if (!cap_sys_admin)
- allowed -= allowed / 32;
+ allowed -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10);
allowed += total_swap_pages;
/*
@@ -3119,3 +3120,24 @@ static int __meminit init_user_reserve(v
return 0;
}
module_init(init_user_reserve)
+
+/*
+ * Initialise sysctl_admin_reserve_kbytes.
+ *
+ * The purpose of sysctl_admin_reserve_kbytes is to allow the sys admin
+ * to log in and kill a memory hogging process.
+ *
+ * Systems with more than 256MB will reserve 8MB, enough to recover
+ * with sshd, bash, and top in OVERCOMMIT_GUESS. Smaller systems will
+ * only reserve 3% of free pages by default.
+ */
+static int __meminit init_admin_reserve(void)
+{
+ unsigned long free_kbytes;
+
+ free_kbytes = global_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
+
+ sysctl_admin_reserve_kbytes = min(free_kbytes / 32, 1UL << 13);
+ return 0;
+}
+module_init(init_admin_reserve)
diff -puN mm/nommu.c~mm-replace-hardcoded-3%-with-admin_reserve_pages-knob mm/nommu.c
--- a/mm/nommu.c~mm-replace-hardcoded-3%-with-admin_reserve_pages-knob
+++ a/mm/nommu.c
@@ -64,6 +64,7 @@ int sysctl_overcommit_ratio = 50; /* def
int sysctl_max_map_count = DEFAULT_MAX_MAP_COUNT;
int sysctl_nr_trim_pages = CONFIG_NOMMU_INITIAL_TRIM_EXCESS;
unsigned long sysctl_user_reserve_kbytes __read_mostly = 1UL << 17; /* 128MB */
+unsigned long sysctl_admin_reserve_kbytes __read_mostly = 1UL << 13; /* 8MB */
int heap_stack_gap = 0;
atomic_long_t mmap_pages_allocated;
@@ -1939,10 +1940,10 @@ int __vm_enough_memory(struct mm_struct
free -= totalreserve_pages;
/*
- * Leave the last 3% for root
+ * Reserve some for root
*/
if (!cap_sys_admin)
- free -= free / 32;
+ free -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10);
if (free > pages)
return 0;
@@ -1952,10 +1953,10 @@ int __vm_enough_memory(struct mm_struct
allowed = totalram_pages * sysctl_overcommit_ratio / 100;
/*
- * Leave the last 3% for root
+ * Reserve some 3% for root
*/
if (!cap_sys_admin)
- allowed -= allowed / 32;
+ allowed -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10);
allowed += total_swap_pages;
/*
@@ -2147,3 +2148,24 @@ static int __meminit init_user_reserve(v
return 0;
}
module_init(init_user_reserve)
+
+/*
+ * Initialise sysctl_admin_reserve_kbytes.
+ *
+ * The purpose of sysctl_admin_reserve_kbytes is to allow the sys admin
+ * to log in and kill a memory hogging process.
+ *
+ * Systems with more than 256MB will reserve 8MB, enough to recover
+ * with sshd, bash, and top in OVERCOMMIT_GUESS. Smaller systems will
+ * only reserve 3% of free pages by default.
+ */
+static int __meminit init_admin_reserve(void)
+{
+ unsigned long free_kbytes;
+
+ free_kbytes = global_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
+
+ sysctl_admin_reserve_kbytes = min(free_kbytes / 32, 1UL << 13);
+ return 0;
+}
+module_init(init_admin_reserve)
_
Patches currently in -mm which might be from agshew@xxxxxxxxx are
origin.patch
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