oomd: increase accuracy of SwapUsedLimit= to permyriads too

oomd.conf has two parameters with fractionals: SwapUsedLimit= and
DefaultMemoryPressureLimit=, but one accepts permyriads, the other only
percentages, for no apparent reason. One carries the "Percent" in the
name, the other doesn't.

Let's clean this up: always accept permyriads, and drop the suffix,
given that it is misleading.

I figure we should internally try to focus on scaling everything
relative to UINT32_MAX, and if that isn't in the cards at least 10000,
but never permille nor percent unless there's a really really good
reason for it (e.g. interface defined by someone else).

7 files changed, 50 insertions, 42 deletions

diff --git a/src/oom/oomd-manager.c b/src/oom/oomd-manager.c
index 65c0bfac61..fad1fb0d45 100644
--- a/src/oom/oomd-manager.c
+++ b/src/oom/oomd-manager.c
@@ -16,7 +16,7 @@ typedef struct ManagedOOMReply {
         ManagedOOMMode mode;
         char *path;
         char *property;
-        unsigned limit;
+        uint32_t limit;
 } ManagedOOMReply;
 
 static void managed_oom_reply_destroy(ManagedOOMReply *reply) {
@@ -53,10 +53,10 @@ static int process_managed_oom_reply(
         assert(m);
 
         static const JsonDispatch dispatch_table[] = {
-                { "mode",     JSON_VARIANT_STRING,   managed_oom_mode,       offsetof(ManagedOOMReply, mode),     JSON_MANDATORY },
-                { "path",     JSON_VARIANT_STRING,   json_dispatch_string,   offsetof(ManagedOOMReply, path),     JSON_MANDATORY },
-                { "property", JSON_VARIANT_STRING,   json_dispatch_string,   offsetof(ManagedOOMReply, property), JSON_MANDATORY },
-                { "limit",    JSON_VARIANT_UNSIGNED, json_dispatch_unsigned, offsetof(ManagedOOMReply, limit),    0 },
+                { "mode",     JSON_VARIANT_STRING,   managed_oom_mode,     offsetof(ManagedOOMReply, mode),     JSON_MANDATORY },
+                { "path",     JSON_VARIANT_STRING,   json_dispatch_string, offsetof(ManagedOOMReply, path),     JSON_MANDATORY },
+                { "property", JSON_VARIANT_STRING,   json_dispatch_string, offsetof(ManagedOOMReply, property), JSON_MANDATORY },
+                { "limit",    JSON_VARIANT_UNSIGNED, json_dispatch_uint32, offsetof(ManagedOOMReply, limit),    0 },
                 {},
         };
 
@@ -87,7 +87,8 @@ static int process_managed_oom_reply(
                 if (ret == -ENOMEM) {
                         r = ret;
                         goto finish;
-                } else if (ret < 0)
+                }
+                if (ret < 0)
                         continue;
 
                 monitor_hm = streq(reply.property, "ManagedOOMSwap") ?
@@ -100,19 +101,15 @@ static int process_managed_oom_reply(
 
                 limit = m->default_mem_pressure_limit;
 
-                if (streq(reply.property, "ManagedOOMMemoryPressure")) {
-                        if (reply.limit > UINT32_MAX) /* out of range */
+                if (streq(reply.property, "ManagedOOMMemoryPressure") && reply.limit > 0) {
+                        int permyriad = UINT32_SCALE_TO_PERMYRIAD(reply.limit);
+
+                        ret = store_loadavg_fixed_point(
+                                        (unsigned long) permyriad / 100,
+                                        (unsigned long) permyriad % 100,
+                                        &limit);
+                        if (ret < 0)
                                 continue;
-                        if (reply.limit != 0) {
-                                int permyriad = UINT32_SCALE_TO_PERMYRIAD(reply.limit);
-
-                                ret = store_loadavg_fixed_point(
-                                                (unsigned long) permyriad / 100,
-                                                (unsigned long) permyriad % 100,
-                                                &limit);
-                                if (ret < 0)
-                                        continue;
-                        }
                 }
 
                 ret = oomd_insert_cgroup_context(NULL, monitor_hm, empty_to_root(reply.path));
@@ -354,11 +351,11 @@ static int monitor_cgroup_contexts_handler(sd_event_source *s, uint64_t usec, vo
                 }
         }
 
-        if (oomd_swap_free_below(&m->system_context, (100 - m->swap_used_limit))) {
+        if (oomd_swap_free_below(&m->system_context, 10000 - m->swap_used_limit_permyriad)) {
                 _cleanup_hashmap_free_ Hashmap *candidates = NULL;
 
-                log_notice("Swap used (%"PRIu64") / total (%"PRIu64") is more than %u%%",
-                        m->system_context.swap_used, m->system_context.swap_total, m->swap_used_limit);
+                log_notice("Swap used (%"PRIu64") / total (%"PRIu64") is more than " PERMYRIAD_AS_PERCENT_FORMAT_STR,
+                           m->system_context.swap_used, m->system_context.swap_total, PERMYRIAD_AS_PERCENT_FORMAT_VAL(m->swap_used_limit_permyriad));
 
                 r = get_monitored_cgroup_contexts_candidates(m->monitored_swap_cgroup_contexts, &candidates);
                 if (r == -ENOMEM)
@@ -484,7 +481,13 @@ static int manager_connect_bus(Manager *m) {
         return 0;
 }
 
-int manager_start(Manager *m, bool dry_run, int swap_used_limit, int mem_pressure_limit_permyriad, usec_t mem_pressure_usec) {
+int manager_start(
+                Manager *m,
+                bool dry_run,
+                int swap_used_limit_permyriad,
+                int mem_pressure_limit_permyriad,
+                usec_t mem_pressure_usec) {
+
         unsigned long l, f;
         int r;
 
@@ -492,10 +495,10 @@ int manager_start(Manager *m, bool dry_run, int swap_used_limit, int mem_pressur
 
         m->dry_run = dry_run;
 
-        m->swap_used_limit = swap_used_limit != -1 ? swap_used_limit : DEFAULT_SWAP_USED_LIMIT;
-        assert(m->swap_used_limit <= 100);
+        m->swap_used_limit_permyriad = swap_used_limit_permyriad >= 0 ? swap_used_limit_permyriad : DEFAULT_SWAP_USED_LIMIT_PERCENT * 100;
+        assert(m->swap_used_limit_permyriad <= 10000);
 
-        if (mem_pressure_limit_permyriad != -1) {
+        if (mem_pressure_limit_permyriad >= 0) {
                 assert(mem_pressure_limit_permyriad <= 10000);
 
                 l = mem_pressure_limit_permyriad / 100;
@@ -543,12 +546,12 @@ int manager_get_dump_string(Manager *m, char **ret) {
 
         fprintf(f,
                 "Dry Run: %s\n"
-                "Swap Used Limit: %u%%\n"
+                "Swap Used Limit: " PERMYRIAD_AS_PERCENT_FORMAT_STR "\n"
                 "Default Memory Pressure Limit: %lu.%02lu%%\n"
                 "Default Memory Pressure Duration: %s\n"
                 "System Context:\n",
                 yes_no(m->dry_run),
-                m->swap_used_limit,
+                PERMYRIAD_AS_PERCENT_FORMAT_VAL(m->swap_used_limit_permyriad),
                 LOAD_INT(m->default_mem_pressure_limit), LOAD_FRAC(m->default_mem_pressure_limit),
                 format_timespan(buf, sizeof(buf), m->default_mem_pressure_duration_usec, USEC_PER_SEC));
         oomd_dump_system_context(&m->system_context, f, "\t");
diff --git a/src/oom/oomd-manager.h b/src/oom/oomd-manager.h
index 50f10021c7..9ab8494c6d 100644
--- a/src/oom/oomd-manager.h
+++ b/src/oom/oomd-manager.h
@@ -18,7 +18,7 @@
  * system.slice are assumed to be less latency sensitive. */
 #define DEFAULT_MEM_PRESSURE_DURATION_USEC (30 * USEC_PER_SEC)
 #define DEFAULT_MEM_PRESSURE_LIMIT_PERCENT 60
-#define DEFAULT_SWAP_USED_LIMIT 90
+#define DEFAULT_SWAP_USED_LIMIT_PERCENT 90
 
 #define RECLAIM_DURATION_USEC (30 * USEC_PER_SEC)
 #define POST_ACTION_DELAY_USEC (15 * USEC_PER_SEC)
@@ -32,7 +32,7 @@ struct Manager {
         Hashmap *polkit_registry;
 
         bool dry_run;
-        unsigned swap_used_limit;
+        int swap_used_limit_permyriad;
         loadavg_t default_mem_pressure_limit;
         usec_t default_mem_pressure_duration_usec;
 
@@ -56,7 +56,7 @@ DEFINE_TRIVIAL_CLEANUP_FUNC(Manager*, manager_free);
 
 int manager_new(Manager **ret);
 
-int manager_start(Manager *m, bool dry_run, int swap_used_limit, int mem_pressure_limit_permyriad, usec_t mem_pressure_usec);
+int manager_start(Manager *m, bool dry_run, int swap_used_limit_permyriad, int mem_pressure_limit_permyriad, usec_t mem_pressure_usec);
 
 int manager_get_dump_string(Manager *m, char **ret);
 
diff --git a/src/oom/oomd-util.c b/src/oom/oomd-util.c
index 9dd9b17c6d..b054ccacc4 100644
--- a/src/oom/oomd-util.c
+++ b/src/oom/oomd-util.c
@@ -134,13 +134,13 @@ bool oomd_memory_reclaim(Hashmap *h) {
         return pgscan_of > last_pgscan_of;
 }
 
-bool oomd_swap_free_below(const OomdSystemContext *ctx, uint64_t threshold_percent) {
+bool oomd_swap_free_below(const OomdSystemContext *ctx, int threshold_permyriad) {
         uint64_t swap_threshold;
 
         assert(ctx);
-        assert(threshold_percent <= 100);
+        assert(threshold_permyriad <= 10000);
 
-        swap_threshold = ctx->swap_total * threshold_percent / ((uint64_t) 100);
+        swap_threshold = ctx->swap_total * threshold_permyriad / (uint64_t) 10000;
         return (ctx->swap_total - ctx->swap_used) < swap_threshold;
 }
 
diff --git a/src/oom/oomd-util.h b/src/oom/oomd-util.h
index bffccf75da..181443ae7a 100644
--- a/src/oom/oomd-util.h
+++ b/src/oom/oomd-util.h
@@ -61,8 +61,8 @@ int oomd_pressure_above(Hashmap *h, usec_t duration, Set **ret);
  * current sum is higher than the last interval's sum (there was some reclaim activity). */
 bool oomd_memory_reclaim(Hashmap *h);
 
-/* Returns true if the amount of swap free is below the percentage of swap specified by `threshold_percent`. */
-bool oomd_swap_free_below(const OomdSystemContext *ctx, uint64_t threshold_percent);
+/* Returns true if the amount of swap free is below the permyriad of swap specified by `threshold_permyriad`. */
+bool oomd_swap_free_below(const OomdSystemContext *ctx, int threshold_permyriad);
 
 /* The compare functions will sort from largest to smallest, putting all the contexts with "avoid" at the end
  * (after the smallest values). */
diff --git a/src/oom/oomd.c b/src/oom/oomd.c
index 2e331e267f..674d53fdcf 100644
--- a/src/oom/oomd.c
+++ b/src/oom/oomd.c
@@ -17,13 +17,13 @@
 #include "signal-util.h"
 
 static bool arg_dry_run = false;
-static int arg_swap_used_limit = -1;
+static int arg_swap_used_limit_permyriad = -1;
 static int arg_mem_pressure_limit_permyriad = -1;
 static usec_t arg_mem_pressure_usec = 0;
 
 static int parse_config(void) {
         static const ConfigTableItem items[] = {
-                { "OOM", "SwapUsedLimitPercent",             config_parse_percent,   0, &arg_swap_used_limit              },
+                { "OOM", "SwapUsedLimit",                    config_parse_permyriad, 0, &arg_swap_used_limit_permyriad    },
                 { "OOM", "DefaultMemoryPressureLimit",       config_parse_permyriad, 0, &arg_mem_pressure_limit_permyriad },
                 { "OOM", "DefaultMemoryPressureDurationSec", config_parse_sec,       0, &arg_mem_pressure_usec            },
                 {}
@@ -159,7 +159,12 @@ static int run(int argc, char *argv[]) {
         if (r < 0)
                 return log_error_errno(r, "Failed to create manager: %m");
 
-        r = manager_start(m, arg_dry_run, arg_swap_used_limit, arg_mem_pressure_limit_permyriad, arg_mem_pressure_usec);
+        r = manager_start(
+                        m,
+                        arg_dry_run,
+                        arg_swap_used_limit_permyriad,
+                        arg_mem_pressure_limit_permyriad,
+                        arg_mem_pressure_usec);
         if (r < 0)
                 return log_error_errno(r, "Failed to start up daemon: %m");
 
diff --git a/src/oom/oomd.conf b/src/oom/oomd.conf
index bd6a9391c6..35ba847457 100644
--- a/src/oom/oomd.conf
+++ b/src/oom/oomd.conf
@@ -12,6 +12,6 @@
 # See oomd.conf(5) for details
 
 [OOM]
-#SwapUsedLimitPercent=90%
+#SwapUsedLimit=90%
 #DefaultMemoryPressureLimit=60%
 #DefaultMemoryPressureDurationSec=30s
diff --git a/src/oom/test-oomd-util.c b/src/oom/test-oomd-util.c
index 49a02f9424..a0e583ac6b 100644
--- a/src/oom/test-oomd-util.c
+++ b/src/oom/test-oomd-util.c
@@ -302,19 +302,19 @@ static void test_oomd_swap_free_below(void) {
                 .swap_total = 20971512 * 1024U,
                 .swap_used = 20971440 * 1024U,
         };
-        assert_se(oomd_swap_free_below(&ctx, 20) == true);
+        assert_se(oomd_swap_free_below(&ctx, 2000) == true);
 
         ctx = (OomdSystemContext) {
                 .swap_total = 20971512 * 1024U,
                 .swap_used = 3310136 * 1024U,
         };
-        assert_se(oomd_swap_free_below(&ctx, 20) == false);
+        assert_se(oomd_swap_free_below(&ctx, 2000) == false);
 
         ctx = (OomdSystemContext) {
                 .swap_total = 0,
                 .swap_used = 0,
         };
-        assert_se(oomd_swap_free_below(&ctx, 20) == false);
+        assert_se(oomd_swap_free_below(&ctx, 2000) == false);
 }
 
 static void test_oomd_sort_cgroups(void) {