top: improve global CPU percentage (smaller & faster code)
diff --git a/procps/Config.in b/procps/Config.in
index cd46a34..fba9e40 100644
--- a/procps/Config.in
+++ b/procps/Config.in
@@ -109,11 +109,11 @@
Make top display CPU usage for each process.
config FEATURE_TOP_CPU_GLOBAL_PERCENTS
- bool "Show CPU global usage percentage (adds 1k byte)"
+ bool "Show CPU global usage percentage (adds 0.5k byte)"
default y
depends on FEATURE_TOP_CPU_USAGE_PERCENTAGE
help
- Makes top display "CPU: n.n% us n.n% sy n.n% ni..." line.
+ Makes top display "CPU: NN% usr NN% sys..." line.
config UPTIME
bool "uptime"
diff --git a/procps/top.c b/procps/top.c
index 6d8dfd8..564e943 100644
--- a/procps/top.c
+++ b/procps/top.c
@@ -292,8 +292,15 @@
/*
* xxx% = (jif.xxx - prev_jif.xxx) / (jif.total - prev_jif.total) * 100%
*/
-#define CALC_STAT(xxx) div_t xxx = div(1000 * (jif.xxx - prev_jif.xxx) / total_diff, 10)
-#define SHOW_STAT(xxx) xxx.quot, '0'+xxx.rem
+ /* using (unsigned) cast to make multiplication cheaper: */
+#define CALC_STAT(xxx) unsigned xxx = 100 * (unsigned)(jif.xxx - prev_jif.xxx) / total_diff
+#define SHOW_STAT(xxx) xxx
+#define FMT "%3u%%"
+// We can display fractional percents, but at least in glibc div() is a _function_
+// and generated code is really awful and big (+0.5k more code):
+//#define CALC_STAT(xxx) div_t xxx = div(1000 * (unsigned)(jif.xxx - prev_jif.xxx) / total_diff, 10)
+//#define SHOW_STAT(xxx) xxx.quot, '0'+xxx.rem
+//#define FMT "%3u.%c%%"
unsigned total_diff = (jif.total - prev_jif.total ? : 1);
CALC_STAT(usr);
CALC_STAT(sys);
@@ -305,10 +312,10 @@
//CALC_STAT(steal);
snprintf(scrbuf, scr_width,
- /* %3u.%c in practice almost never displays "100.0"
- * and thus has implicit leading space: " 99.6" */
- "CPU:%3u.%c%% us%3u.%c%% sy%3u.%c%% ni%3u.%c%% id%3u.%c%% wa%3u.%c%% hi%3u.%c%% si",
- // %3u.%c%%st", - what is this 'steal' thing?
+ /* %3u in practice almost never displays "100"
+ * and thus has implicit leading space: " 99" */
+ "CPU:"FMT" usr"FMT" sys"FMT" nice"FMT" idle"FMT" wait"FMT" irq"FMT" softirq",
+ // FMT" steal", - what is this 'steal' thing?
// I doubt anyone needs to know it
SHOW_STAT(usr), SHOW_STAT(sys), SHOW_STAT(nic), SHOW_STAT(idle),
SHOW_STAT(iowait), SHOW_STAT(irq), SHOW_STAT(softirq)
@@ -317,6 +324,7 @@
puts(scrbuf);
#undef SHOW_STAT
#undef CALC_STAT
+#undef FMT
}
snprintf(scrbuf, scr_width, "Load average: %s", buf);