oomd: new helper oomd_update_cgroup_contexts_between_hashmaps

src/oom/oomd-util.c

@@ -413,6 +413,25 @@ int oomd_insert_cgroup_context(Hashmap *old_h, Hashmap *new_h, const char *path)
         return 0;
 }
 
+void oomd_update_cgroup_contexts_between_hashmaps(Hashmap *old_h, Hashmap *curr_h) {
+        OomdCGroupContext *ctx;
+
+        assert(old_h);
+        assert(curr_h);
+
+        HASHMAP_FOREACH(ctx, curr_h) {
+                OomdCGroupContext *old_ctx;
+
+                old_ctx = hashmap_get(old_h, ctx->path);
+                if (!old_ctx)
+                        continue;
+
+                ctx->last_pgscan = old_ctx->pgscan;
+                ctx->mem_pressure_limit = old_ctx->mem_pressure_limit;
+                ctx->last_hit_mem_pressure_limit = old_ctx->last_hit_mem_pressure_limit;
+        }
+}
+
 void oomd_dump_swap_cgroup_context(const OomdCGroupContext *ctx, FILE *f, const char *prefix) {
         char swap[FORMAT_BYTES_MAX];
 

src/oom/oomd-util.h

@@ -119,6 +119,9 @@ int oomd_system_context_acquire(const char *proc_swaps_path, OomdSystemContext *
  * was no prior data to reference. */
 int oomd_insert_cgroup_context(Hashmap *old_h, Hashmap *new_h, const char *path);
 
+/* Update each OomdCGroupContext in `curr_h` with prior interval information from `old_h`. */
+void oomd_update_cgroup_contexts_between_hashmaps(Hashmap *old_h, Hashmap *curr_h);
+
 void oomd_dump_swap_cgroup_context(const OomdCGroupContext *ctx, FILE *f, const char *prefix);
 void oomd_dump_memory_pressure_cgroup_context(const OomdCGroupContext *ctx, FILE *f, const char *prefix);
 void oomd_dump_system_context(const OomdSystemContext *ctx, FILE *f, const char *prefix);

src/oom/test-oomd-util.c

@@ -176,6 +176,53 @@ static void test_oomd_cgroup_context_acquire_and_insert(void) {
         }
 }
 
+static void test_oomd_update_cgroup_contexts_between_hashmaps(void) {
+        _cleanup_hashmap_free_ Hashmap *h_old = NULL, *h_new = NULL;
+        OomdCGroupContext *c_old, *c_new;
+        char **paths = STRV_MAKE("/0.slice",
+                                 "/1.slice");
+
+        OomdCGroupContext ctx_old[3] = {
+                { .path = paths[0],
+                  .mem_pressure_limit = 5,
+                  .last_hit_mem_pressure_limit = 777,
+                  .pgscan = 57 },
+                { .path = paths[1],
+                  .mem_pressure_limit = 6,
+                  .last_hit_mem_pressure_limit = 888,
+                  .pgscan = 42 },
+        };
+
+        OomdCGroupContext ctx_new[3] = {
+                { .path = paths[0],
+                  .pgscan = 100 },
+                { .path = paths[1],
+                  .pgscan = 101 },
+        };
+
+        assert_se(h_old = hashmap_new(&string_hash_ops));
+        assert_se(hashmap_put(h_old, paths[0], &ctx_old[0]) >= 0);
+        assert_se(hashmap_put(h_old, paths[1], &ctx_old[1]) >= 0);
+
+        assert_se(h_new = hashmap_new(&string_hash_ops));
+        assert_se(hashmap_put(h_new, paths[0], &ctx_new[0]) >= 0);
+        assert_se(hashmap_put(h_new, paths[1], &ctx_new[1]) >= 0);
+
+        oomd_update_cgroup_contexts_between_hashmaps(h_old, h_new);
+
+        assert_se(c_old = hashmap_get(h_old, "/0.slice"));
+        assert_se(c_new = hashmap_get(h_new, "/0.slice"));
+        assert_se(c_old->pgscan == c_new->last_pgscan);
+        assert_se(c_old->mem_pressure_limit == c_new->mem_pressure_limit);
+        assert_se(c_old->last_hit_mem_pressure_limit == c_new->last_hit_mem_pressure_limit);
+
+        assert_se(c_old = hashmap_get(h_old, "/1.slice"));
+        assert_se(c_new = hashmap_get(h_new, "/1.slice"));
+        assert_se(c_old->pgscan == c_new->last_pgscan);
+        assert_se(c_old->mem_pressure_limit == c_new->mem_pressure_limit);
+        assert_se(c_old->last_hit_mem_pressure_limit == c_new->last_hit_mem_pressure_limit);
+}
+
 static void test_oomd_system_context_acquire(void) {
         _cleanup_(unlink_tempfilep) char path[] = "/oomdgetsysctxtestXXXXXX";
         OomdSystemContext ctx;
@@ -395,6 +442,7 @@ int main(void) {
 
         test_setup_logging(LOG_DEBUG);
 
+        test_oomd_update_cgroup_contexts_between_hashmaps();
         test_oomd_system_context_acquire();
         test_oomd_pressure_above();
         test_oomd_memory_reclaim();