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Change a variable name and space out RateMeter::update to make it easier to understand.

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david
2008-04-24 20:32:47 +00:00
parent 5a8e417c0c
commit 6982bacef5
1 changed files with 18 additions and 13 deletions
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31
timing.cc
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@@ -313,7 +313,7 @@ double RateMeter::getCurrentByteRate(const struct timeval *now, bool update) {
void RateMeter::update(u32 packets, u32 bytes, const struct timeval *now) {
struct timeval tv;
double diff;
double d;
double interval;
double count;
assert(isSet(&start_tv));
@@ -333,8 +333,11 @@ void RateMeter::update(u32 packets, u32 bytes, const struct timeval *now) {
/* Calculate approximate moving averages of how many packets and bytes were
recorded in the last CURRENT_RATE_HISTORY seconds. These averages are what
are returned as the "current" rates. */
/* How long since the last update? */
diff = TIMEVAL_SUBTRACT(*now, last_update_tv) / 1000000.0;
assert(diff >= 0.0);
/* Find out how far back in time to look. We want to look back
CURRENT_RATE_HISTORY seconds, or to when the last update occurred,
whichever is longer. However, we never look past the start. */
@@ -343,26 +346,28 @@ void RateMeter::update(u32 packets, u32 bytes, const struct timeval *now) {
threshold for deciding how far back to look. */
TIMEVAL_ADD(tmp, start_tv, (time_t) (CURRENT_RATE_HISTORY * 1000000.0));
if (TIMEVAL_AFTER(*now, tmp))
d = MAX(CURRENT_RATE_HISTORY, diff);
interval = MAX(CURRENT_RATE_HISTORY, diff);
else
d = TIMEVAL_SUBTRACT(*now, start_tv) / 1000000.0;
assert(d >= 0);
interval = TIMEVAL_SUBTRACT(*now, start_tv) / 1000000.0;
assert(diff <= interval);
/* If we get packets in the very same instant that the timer is started,
there's no way to calculate meaningful rates. Ignore it. */
if (d == 0.0)
if (interval == 0.0)
return;
/* To calculate the approximate average of the packet rate over the last d
seconds, we assume that the rate was constant over that interval. We
calculate how many packets would have been received in that interval,
ignoring the first diff seconds' worth, (d - diff) * current_packet_rate.
/* To calculate the approximate average of the packet rate over the last
interval seconds, we assume that the rate was constant over that interval.
We calculate how many packets would have been received in that interval,
ignoring the first diff seconds' worth:
(interval - diff) * current_packet_rate.
Then we add how many packets were received in the most recent diff seconds.
Divide by the width of the interval to get the average. */
count = (d - diff) * current_packet_rate + packets;
current_packet_rate = count / d;
count = (interval - diff) * current_packet_rate + packets;
current_packet_rate = count / interval;
assert(current_packet_rate >= 0.0);
/* Likewise with the byte rate. */
count = (d - diff) * current_byte_rate + bytes;
current_byte_rate = count / d;
count = (interval - diff) * current_byte_rate + bytes;
current_byte_rate = count / interval;
assert(current_byte_rate >= 0.0);
last_update_tv = *now;