Merge pull request #24126 from inknos/issue-23824

Docker compat: Return null when swappiness is unset instead of -1

Author: Luap99

docs/source/markdown/podman-container-inspect.1.md.in

@@ -296,7 +296,7 @@ $ podman container inspect foobar
             "KernelMemory": 0,
             "MemoryReservation": 0,
             "MemorySwap": 0,
-            "MemorySwappiness": 0,
+            "MemorySwappiness": null,
             "OomKillDisable": false,
             "PidsLimit": 2048,
             "Ulimits": [],

libpod/container_inspect_linux.go

@@ -61,10 +61,8 @@ func (c *Container) platformInspectContainerHostConfig(ctrSpec *spec.Spec, hostC
 					hostConfig.MemorySwap = *ctrSpec.Linux.Resources.Memory.Swap
 				}
 				if ctrSpec.Linux.Resources.Memory.Swappiness != nil {
-					hostConfig.MemorySwappiness = int64(*ctrSpec.Linux.Resources.Memory.Swappiness)
-				} else {
-					// Swappiness has a default of -1
-					hostConfig.MemorySwappiness = -1
+					swappiness := int64(*ctrSpec.Linux.Resources.Memory.Swappiness)
+					hostConfig.MemorySwappiness = &swappiness
 				}
 				if ctrSpec.Linux.Resources.Memory.DisableOOMKiller != nil {
 					hostConfig.OomKillDisable = *ctrSpec.Linux.Resources.Memory.DisableOOMKiller

libpod/define/container_inspect.go

@@ -643,8 +643,8 @@ type InspectContainerHostConfig struct {
 	// MemorySwappiness is the willingness of the kernel to page container
 	// memory to swap. It is an integer from 0 to 100, with low numbers
 	// being more likely to be put into swap.
-	// -1, the default, will not set swappiness and use the system defaults.
-	MemorySwappiness int64 `json:"MemorySwappiness"`
+	// nil means swappiness is unset and the system default is used.
+	MemorySwappiness *int64 `json:"MemorySwappiness"`
 	// OomKillDisable indicates whether the kernel OOM killer is disabled
 	// for the container.
 	OomKillDisable bool `json:"OomKillDisable"`

test/apiv2/20-containers.at

@@ -870,6 +870,21 @@ t GET containers/$cid/json 200 \
 t DELETE containers/$cid 204
 podman rmi test1
 
+# test MemorySwappiness
+podman run -d --rm --name swappiness_with_mem_limit --memory 200M $IMAGE top
+podman run -d --rm --name swappiness_without_mem_limit $IMAGE top
+
+t GET containers/swappiness_with_mem_limit/json 200 \
+  .HostConfig.MemorySwappiness=null
+t GET containers/swappiness_without_mem_limit/json 200 \
+  .HostConfig.MemorySwappiness=null
+
+t GET libpod/containers/swappiness_with_mem_limit/json 200 \
+  .HostConfig.MemorySwappiness=null
+t GET libpod/containers/swappiness_without_mem_limit/json 200 \
+  .HostConfig.MemorySwappiness=null
+
+podman stop -t0 swappiness_with_mem_limit swappiness_without_mem_limit
 
 # test if API support -1 for ulimits https://github.com/containers/podman/issues/24886
 

test/e2e/container_clone_test.go

@@ -140,7 +140,7 @@ var _ = Describe("Podman container clone", func() {
 		cloneInspect.WaitWithDefaultTimeout()
 		Expect(cloneInspect).To(ExitCleanly())
 		cloneData = cloneInspect.InspectContainerToJSON()
-		Expect(cloneData[0].HostConfig).To(HaveField("MemorySwappiness", int64(0)))
+		Expect(cloneData[0].HostConfig.MemorySwappiness).To(BeNil())
 	})
 
 	It("podman container clone in a pod", func() {