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

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This commit is contained in:
Denis Vlasenko 2007-06-10 18:04:54 +00:00
parent 5a65447e30
commit b1e5addfed
2 changed files with 16 additions and 8 deletions
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4
procps/Config.in
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@ -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"

20
procps/top.c
View File

@ -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);