Make Linux memory allocations int64 not uint64

The kernel ABI to these values is a string, which accepts the value `-1` to mean "unlimited" or an integer up to 2^63 for an amount of memory in bytes. While the internal representation in the kernel is unsigned, this is not exposed in any ABI directly. Because of the user-kernel memory split, values over 2^63 are not really useful; indeed that much memory is not supported, as physical memory is limited to 52 bits in the forthcoming switch to five level page tables. So it is much more natural to support the value `-1` for unlimited, especially as the actual number needed to represent the maximum has varied in different kernel versions, and across 32 and 64 bit architectures, so determining the value to use is not possible, so it is necessary to write the string `-1` to the cgroup files. See also discussion in - opencontainers/runc#1494 - opencontainers/runc#1492 - opencontainers/runc#1375 - opencontainers/runc#1421 Signed-off-by: Justin Cormack <[email protected]>
wking · Jun 23, 2017 · e73cd70 · e73cd70
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diff --git a/config-linux.md b/config-linux.md
@@ -270,13 +270,16 @@ For more information, see the kernel cgroups documentation about [memory][cgroup
 **`memory`** (object, OPTIONAL) represents the cgroup subsystem `memory` and it's used to set limits on the container's memory usage.
 For more information, see the kernel cgroups documentation about [memory][cgroup-v1-memory].
 
-The following parameters can be specified to set up the controller:
+Values for memory specify the limit in bytes, or `-1` for unlimited memory.
+
+* **`limit`** *(int64, OPTIONAL)* - sets limit of memory usage
+* **`reservation`** *(int64, OPTIONAL)* - sets soft limit of memory usage
+* **`swap`** *(int64, OPTIONAL)* - sets limit of memory+Swap usage
+* **`kernel`** *(int64, OPTIONAL)* - sets hard limit for kernel memory
+* **`kernelTCP`** *(int64, OPTIONAL)* - sets hard limit for kernel TCP buffer memory
+
+For `swappiness` the values are from 0 to 100. Higher means more swappy.
 
-* **`limit`** *(uint64, OPTIONAL)* - sets limit of memory usage in bytes
-* **`reservation`** *(uint64, OPTIONAL)* - sets soft limit of memory usage in bytes
-* **`swap`** *(uint64, OPTIONAL)* - sets limit of memory+Swap usage
-* **`kernel`** *(uint64, OPTIONAL)* - sets hard limit for kernel memory
-* **`kernelTCP`** *(uint64, OPTIONAL)* - sets hard limit in bytes for kernel TCP buffer memory
 * **`swappiness`** *(uint64, OPTIONAL)* - sets swappiness parameter of vmscan (See sysctl's vm.swappiness)
 
 #### Example
@@ -286,8 +289,8 @@ The following parameters can be specified to set up the controller:
         "limit": 536870912,
         "reservation": 536870912,
         "swap": 536870912,
-        "kernel": 0,
-        "kernelTCP": 0,
+        "kernel": -1,
+        "kernelTCP": -1,
         "swappiness": 0
     }
 ```

diff --git a/config.md b/config.md
@@ -689,8 +689,8 @@ Here is a full example `config.json` for reference.
                 "limit": 536870912,
                 "reservation": 536870912,
                 "swap": 536870912,
-                "kernel": 0,
-                "kernelTCP": 0,
+                "kernel": -1,
+                "kernelTCP": -1,
                 "swappiness": 0
             },
             "cpu": {

diff --git a/schema/config-linux.json b/schema/config-linux.json
@@ -172,23 +172,23 @@
                         "properties": {
                             "kernel": {
                                 "id": "https://opencontainers.org/schema/bundle/linux/resources/memory/kernel",
-                                "$ref": "defs.json#/definitions/uint64"
+                                "$ref": "defs.json#/definitions/int64"
                             },
                             "kernelTCP": {
                                 "id": "https://opencontainers.org/schema/bundle/linux/resources/memory/kernelTCP",
-                                "$ref": "defs.json#/definitions/uint64"
+                                "$ref": "defs.json#/definitions/int64"
                             },
                             "limit": {
                                 "id": "https://opencontainers.org/schema/bundle/linux/resources/memory/limit",
-                                "$ref": "defs.json#/definitions/uint64"
+                                "$ref": "defs.json#/definitions/int64"
                             },
                             "reservation": {
                                 "id": "https://opencontainers.org/schema/bundle/linux/resources/memory/reservation",
-                                "$ref": "defs.json#/definitions/uint64"
+                                "$ref": "defs.json#/definitions/int64"
                             },
                             "swap": {
                                 "id": "https://opencontainers.org/schema/bundle/linux/resources/memory/swap",
-                                "$ref": "defs.json#/definitions/uint64"
+                                "$ref": "defs.json#/definitions/int64"
                             },
                             "swappiness": {
                                 "id": "https://opencontainers.org/schema/bundle/linux/resources/memory/swappiness",

diff --git a/schema/test/config/good/spec-example.json b/schema/test/config/good/spec-example.json
@@ -239,8 +239,8 @@
                 "limit": 536870912,
                 "reservation": 536870912,
                 "swap": 536870912,
-                "kernel": 0,
-                "kernelTCP": 0,
+                "kernel": -1,
+                "kernelTCP": -1,
                 "swappiness": 0
             },
             "cpu": {

diff --git a/specs-go/config.go b/specs-go/config.go
@@ -273,15 +273,15 @@ type LinuxBlockIO struct {
 // LinuxMemory for Linux cgroup 'memory' resource management
 type LinuxMemory struct {
 	// Memory limit (in bytes).
-	Limit *uint64 `json:"limit,omitempty"`
+	Limit *int64 `json:"limit,omitempty"`
 	// Memory reservation or soft_limit (in bytes).
-	Reservation *uint64 `json:"reservation,omitempty"`
+	Reservation *int64 `json:"reservation,omitempty"`
 	// Total memory limit (memory + swap).
-	Swap *uint64 `json:"swap,omitempty"`
+	Swap *int64 `json:"swap,omitempty"`
 	// Kernel memory limit (in bytes).
-	Kernel *uint64 `json:"kernel,omitempty"`
+	Kernel *int64 `json:"kernel,omitempty"`
 	// Kernel memory limit for tcp (in bytes)
-	KernelTCP *uint64 `json:"kernelTCP,omitempty"`
+	KernelTCP *int64 `json:"kernelTCP,omitempty"`
 	// How aggressive the kernel will swap memory pages.
 	Swappiness *uint64 `json:"swappiness,omitempty"`
 }