diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt
index 1fbd4eb7b64aff335bed40a3d9ebbde95a26bcc1..9f5481bdc5a43f942fb833f3131901249d2d5c50 100644
--- a/Documentation/sysctl/vm.txt
+++ b/Documentation/sysctl/vm.txt
@@ -47,6 +47,7 @@ Currently, these files are in /proc/sys/vm:
- numa_zonelist_order
- oom_dump_tasks
- oom_kill_allocating_task
+- overcommit_kbytes
- overcommit_memory
- overcommit_ratio
- page-cluster
@@ -574,6 +575,17 @@ The default value is 0.
==============================================================
+overcommit_kbytes:
+
+When overcommit_memory is set to 2, the committed address space is not
+permitted to exceed swap plus this amount of physical RAM. See below.
+
+Note: overcommit_kbytes is the counterpart of overcommit_ratio. Only one
+of them may be specified at a time. Setting one disables the other (which
+then appears as 0 when read).
+
+==============================================================
+
overcommit_memory:
This value contains a flag that enables memory overcommitment.
diff --git a/Documentation/vm/overcommit-accounting b/Documentation/vm/overcommit-accounting
index 8eaa2fc4b8fae253930a798f38394438198dbf5a..cbfaaa674118daaf46e6467cf865d4cd06aae23e 100644
--- a/Documentation/vm/overcommit-accounting
+++ b/Documentation/vm/overcommit-accounting
@@ -14,8 +14,8 @@ The Linux kernel supports the following overcommit handling modes
2 - Don't overcommit. The total address space commit
for the system is not permitted to exceed swap + a
- configurable percentage (default is 50) of physical RAM.
- Depending on the percentage you use, in most situations
+ configurable amount (default is 50%) of physical RAM.
+ Depending on the amount you use, in most situations
this means a process will not be killed while accessing
pages but will receive errors on memory allocation as
appropriate.
@@ -26,7 +26,8 @@ The Linux kernel supports the following overcommit handling modes
The overcommit policy is set via the sysctl `vm.overcommit_memory'.
-The overcommit percentage is set via `vm.overcommit_ratio'.
+The overcommit amount can be set via `vm.overcommit_ratio' (percentage)
+or `vm.overcommit_kbytes' (absolute value).
The current overcommit limit and amount committed are viewable in
/proc/meminfo as CommitLimit and Committed_AS respectively.
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 4c0c01afc19b8fdf535de0dfc2a5ff22d07db22f..a512dd836931c1f8fc336e6a61c0175c8e270dbc 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -57,6 +57,15 @@ extern int sysctl_legacy_va_layout;
extern unsigned long sysctl_user_reserve_kbytes;
extern unsigned long sysctl_admin_reserve_kbytes;
+extern int sysctl_overcommit_memory;
+extern int sysctl_overcommit_ratio;
+extern unsigned long sysctl_overcommit_kbytes;
+
+extern int overcommit_ratio_handler(struct ctl_table *, int, void __user *,
+ size_t *, loff_t *);
+extern int overcommit_kbytes_handler(struct ctl_table *, int, void __user *,
+ size_t *, loff_t *);
+
#define nth_page(page,n) pfn_to_page(page_to_pfn((page)) + (n))
/* to align the pointer to the (next) page boundary */
diff --git a/include/linux/mman.h b/include/linux/mman.h
index 7f7f8dae4b1deec32eb1079428f4b13b87dd25c7..16373c8f5f5788c12a2b404d3793f0dd67d979c5 100644
--- a/include/linux/mman.h
+++ b/include/linux/mman.h
@@ -9,6 +9,7 @@
extern int sysctl_overcommit_memory;
extern int sysctl_overcommit_ratio;
+extern unsigned long sysctl_overcommit_kbytes;
extern struct percpu_counter vm_committed_as;
#ifdef CONFIG_SMP
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index c8da99f905cf522a34dd7ff059bde584e4d8c90a..332cefcdb04b4a004b280aebdd4d7de61a036dea 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -95,8 +95,6 @@
#if defined(CONFIG_SYSCTL)
/* External variables not in a header file. */
-extern int sysctl_overcommit_memory;
-extern int sysctl_overcommit_ratio;
extern int max_threads;
extern int suid_dumpable;
#ifdef CONFIG_COREDUMP
@@ -1121,7 +1119,14 @@ static struct ctl_table vm_table[] = {
.data = &sysctl_overcommit_ratio,
.maxlen = sizeof(sysctl_overcommit_ratio),
.mode = 0644,
- .proc_handler = proc_dointvec,
+ .proc_handler = overcommit_ratio_handler,
+ },
+ {
+ .procname = "overcommit_kbytes",
+ .data = &sysctl_overcommit_kbytes,
+ .maxlen = sizeof(sysctl_overcommit_kbytes),
+ .mode = 0644,
+ .proc_handler = overcommit_kbytes_handler,
},
{
.procname = "page-cluster",
diff --git a/mm/mmap.c b/mm/mmap.c
index 834b2d785f1e2f2fdce59a608f28a94b02b5d82d..39552de6e1db11c9c60f4a53df9b1739afec3320 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -86,6 +86,7 @@ EXPORT_SYMBOL(vm_get_page_prot);
int sysctl_overcommit_memory __read_mostly = OVERCOMMIT_GUESS; /* heuristic overcommit */
int sysctl_overcommit_ratio __read_mostly = 50; /* default is 50% */
+unsigned long sysctl_overcommit_kbytes __read_mostly;
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 */
diff --git a/mm/nommu.c b/mm/nommu.c
index fec093adad9c1d65799206805f3d95fe19a1da88..8740213b1647019c9fdbaaf355da3f2e5e632d99 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -60,6 +60,7 @@ unsigned long highest_memmap_pfn;
struct percpu_counter vm_committed_as;
int sysctl_overcommit_memory = OVERCOMMIT_GUESS; /* heuristic overcommit */
int sysctl_overcommit_ratio = 50; /* default is 50% */
+unsigned long sysctl_overcommit_kbytes __read_mostly;
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 */
diff --git a/mm/util.c b/mm/util.c
index 808f375648e77b6c1057aeee2c6d19ea26af981e..a24aa22f2473690c1e2fa95514f778c6c0c616a7 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -404,13 +404,45 @@ struct address_space *page_mapping(struct page *page)
return mapping;
}
+int overcommit_ratio_handler(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp,
+ loff_t *ppos)
+{
+ int ret;
+
+ ret = proc_dointvec(table, write, buffer, lenp, ppos);
+ if (ret == 0 && write)
+ sysctl_overcommit_kbytes = 0;
+ return ret;
+}
+
+int overcommit_kbytes_handler(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp,
+ loff_t *ppos)
+{
+ int ret;
+
+ ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
+ if (ret == 0 && write)
+ sysctl_overcommit_ratio = 0;
+ return ret;
+}
+
/*
* Committed memory limit enforced when OVERCOMMIT_NEVER policy is used
*/
unsigned long vm_commit_limit(void)
{
- return ((totalram_pages - hugetlb_total_pages())
- * sysctl_overcommit_ratio / 100) + total_swap_pages;
+ unsigned long allowed;
+
+ if (sysctl_overcommit_kbytes)
+ allowed = sysctl_overcommit_kbytes >> (PAGE_SHIFT - 10);
+ else
+ allowed = ((totalram_pages - hugetlb_total_pages())
+ * sysctl_overcommit_ratio / 100);
+ allowed += total_swap_pages;
+
+ return allowed;
}