{Memory,Swap}Meter: add "compressed memory" metrics

For now, the semantics are mostly fit for Linux zswap subsystem. For
instance, we add the third swap usage metric that indicates the amount
of memory that is accounted to swap but in fact stored elsewhere. This
exactly matches the definition of frontswap/zswap, and is probably of
little use to all other platforms.

1 files changed, 17 insertions, 2 deletions

diff --git a/MemoryMeter.c b/MemoryMeter.c
index 1dad1356..28c0be27 100644
--- a/MemoryMeter.c
+++ b/MemoryMeter.c
@@ -20,6 +20,7 @@ static const int MemoryMeter_attributes[] = {
    MEMORY_USED,
    MEMORY_BUFFERS,
    MEMORY_SHARED,
+   MEMORY_COMPRESSED,
    MEMORY_CACHE
 };
 
@@ -28,8 +29,9 @@ static void MemoryMeter_updateValues(Meter* this) {
    size_t size = sizeof(this->txtBuffer);
    int written;
 
-   /* shared and available memory are not supported on all platforms */
+   /* shared, compressed and available memory are not supported on all platforms */
    this->values[MEMORY_METER_SHARED] = NAN;
+   this->values[MEMORY_METER_COMPRESSED] = NAN;
    this->values[MEMORY_METER_AVAILABLE] = NAN;
    Platform_setMemoryValues(this);
 
@@ -38,7 +40,13 @@ static void MemoryMeter_updateValues(Meter* this) {
       "MEMORY_METER_AVAILABLE is not the last item in MemoryMeterValues");
    this->curItems = MEMORY_METER_AVAILABLE;
 
-   written = Meter_humanUnit(buffer, this->values[MEMORY_METER_USED], size);
+   /* we actually want to show "used + compressed" */
+   double used = this->values[MEMORY_METER_USED];
+   if (!isnan(this->values[MEMORY_METER_COMPRESSED])) {
+      used += this->values[MEMORY_METER_COMPRESSED];
+   }
+
+   written = Meter_humanUnit(buffer, used, size);
    METER_BUFFER_CHECK(buffer, size, written);
 
    METER_BUFFER_APPEND_CHR(buffer, size, '/');
@@ -69,6 +77,13 @@ static void MemoryMeter_display(const Object* cast, RichString* out) {
       RichString_appendAscii(out, CRT_colors[MEMORY_SHARED], buffer);
    }
 
+   /* compressed memory is not supported on all platforms */
+   if (!isnan(this->values[MEMORY_METER_COMPRESSED])) {
+      Meter_humanUnit(buffer, this->values[MEMORY_METER_COMPRESSED], sizeof(buffer));
+      RichString_appendAscii(out, CRT_colors[METER_TEXT], " compressed:");
+      RichString_appendAscii(out, CRT_colors[MEMORY_COMPRESSED], buffer);
+   }
+
    Meter_humanUnit(buffer, this->values[MEMORY_METER_CACHE], sizeof(buffer));
    RichString_appendAscii(out, CRT_colors[METER_TEXT], " cache:");
    RichString_appendAscii(out, CRT_colors[MEMORY_CACHE], buffer);