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progress: simplify performance measurement by using getnanotime()

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Calculating duration from a single uint64_t is simpler than from a struct
timeval. Change throughput measurement from gettimeofday() to
getnanotime().

Also calculate misec only if needed, and change integer division to integer
multiplication + shift, which should be slightly faster.

Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Karsten Blees 2014-07-12 02:08:11 +02:00 committed by Junio C Hamano
parent 132d41e69a
commit 83d26fa724
1 changed files with 36 additions and 35 deletions
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41
progress.c
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@ -12,13 +12,14 @@
#include "gettext.h"
#include "progress.h"
#include "strbuf.h"
#include "trace.h"
#define TP_IDX_MAX 8
struct throughput {
off_t curr_total;
off_t prev_total;
struct timeval prev_tv;
uint64_t prev_ns;
unsigned int avg_bytes;
unsigned int avg_misecs;
unsigned int last_bytes[TP_IDX_MAX];
@ -127,50 +128,51 @@ static void throughput_string(struct strbuf *buf, off_t total,
void display_throughput(struct progress *progress, off_t total)
{
struct throughput *tp;
struct timeval tv;
unsigned int misecs;
uint64_t now_ns;
unsigned int misecs, count, rate;
struct strbuf buf = STRBUF_INIT;
if (!progress)
return;
tp = progress->throughput;
gettimeofday(&tv, NULL);
now_ns = getnanotime();
if (!tp) {
progress->throughput = tp = calloc(1, sizeof(*tp));
if (tp) {
tp->prev_total = tp->curr_total = total;
tp->prev_tv = tv;
tp->prev_ns = now_ns;
}
return;
}
tp->curr_total = total;
/* only update throughput every 0.5 s */
if (now_ns - tp->prev_ns <= 500000000)
return;
/*
* We have x = bytes and y = microsecs. We want z = KiB/s:
* We have x = bytes and y = nanosecs. We want z = KiB/s:
*
* z = (x / 1024) / (y / 1000000)
* z = x / y * 1000000 / 1024
* z = x / (y * 1024 / 1000000)
* z = (x / 1024) / (y / 1000000000)
* z = x / y * 1000000000 / 1024
* z = x / (y * 1024 / 1000000000)
* z = x / y'
*
* To simplify things we'll keep track of misecs, or 1024th of a sec
* obtained with:
*
* y' = y * 1024 / 1000000
* y' = y / (1000000 / 1024)
* y' = y / 977
* y' = y * 1024 / 1000000000
* y' = y * (2^10 / 2^42) * (2^42 / 1000000000)
* y' = y / 2^32 * 4398
* y' = (y * 4398) >> 32
*/
misecs = (tv.tv_sec - tp->prev_tv.tv_sec) * 1024;
misecs += (int)(tv.tv_usec - tp->prev_tv.tv_usec) / 977;
if (misecs > 512) {
struct strbuf buf = STRBUF_INIT;
unsigned int count, rate;
misecs = ((now_ns - tp->prev_ns) * 4398) >> 32;
count = total - tp->prev_total;
tp->prev_total = total;
tp->prev_tv = tv;
tp->prev_ns = now_ns;
tp->avg_bytes += count;
tp->avg_misecs += misecs;
rate = tp->avg_bytes / tp->avg_misecs;
@ -186,7 +188,6 @@ void display_throughput(struct progress *progress, off_t total)
if (progress->last_value != -1 && progress_update)
display(progress, progress->last_value, NULL);
}
}
int display_progress(struct progress *progress, unsigned n)
{