top: improve global CPU percentage (smaller & faster code)

diff --git a/procps/Config.in b/procps/Config.in
index cd46a3448daee88658c013e10a305d9f4b6f4b71..fba9e40746896d3d126096497b9767d0e14e4662 100644 (file)
--- a/procps/Config.in
+++ b/procps/Config.in
@@ -109,11 +109,11 @@ config FEATURE_TOP_CPU_USAGE_PERCENTAGE
          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 6d8dfd880f0a18b7e864adc854041de2c6061b2f..564e94343e3fbe5dc0324393450b3620e9182e76 100644 (file)
--- a/procps/top.c
+++ b/procps/top.c
@@ -292,8 +292,15 @@ static unsigned long display_generic(int scr_width)
                /*
                 * 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 @@ static unsigned long display_generic(int scr_width)
                //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 @@ static unsigned long display_generic(int scr_width)
                puts(scrbuf);
 #undef SHOW_STAT
 #undef CALC_STAT
+#undef FMT
        }
 
        snprintf(scrbuf, scr_width, "Load average: %s", buf);