Source code and discussion follow below.
Over the last 24 hours I've polled some URLs each 10 minutes and
measured the response time. This is a statistics report:
min avg max (count) <2 2-5 5-15 >15 URL - response times in seconds
0.75 2.00 11.79 ( 144) 68% 27% 4% 0% http://pl.wikipedia.com/wiki.cgi?Szwecja
0.56 2.70 89.78 ( 144) 95% 0% 0% 3% http://www.wikipedia.com/wiki.png
1.47 2.90 8.63 ( 144) 27% 64% 7% 0% http://pl.wikipedia.com/wiki.cgi?Ostatnie_zmiany
1.36 2.98 28.68 ( 144) 30% 62% 6% 0% http://pl.wikipedia.com/
0.83 3.21 91.86 ( 144) 94% 0% 0% 4% http://eo.wikipedia.com/vikio.png
1.00 4.45 140.53 ( 144) 63% 29% 2% 4% http://eo.wikipedia.com/wiki/Svedio
1.08 5.70 137.43 ( 144) 53% 34% 7% 4% http://eo.wikipedia.com/
3.40 7.09 68.23 ( 144) 0% 38% 56% 4% http://eo.wikipedia.com/wiki/Lastaj_Sxangxoj
3.35 13.59 203.39 ( 144) 0% 18% 63% 18% http://www.wikipedia.com/wiki/special:RecentChanges
1.61 28.38 411.43 ( 144) 4% 23% 33% 38% http://www.wikipedia.com/wiki/Sweden
3.86 45.16 359.17 ( 144) 0% 2% 38% 58% http://www.wikipedia.com/
The first three columns present the minimum, average, and maximum
response times. The rows are sorted on the average column. As you
can see the minimums are very good: 0.56 seconds roundtrip from Sweden
to San Diego is excellent. Even the English Wikipedia start page
(with the worst average in the list) has been served on 3.86 seconds,
which is quite good (this happened 6:10 am GMT). However, the
striking numbers are the maximum response times of several minutes.
The fourth column is the number of samples, which is 144 in 24 hours.
The following four columns present the statistical distribution of
samples in four categories: The percentage of samples that were less
than 2 seconds, those between 2 and 5 seconds, those between 5 and 15
seconds, and those in excess of 15 seconds. I thing usability gurus
like Jakob Nielsen has declared that 5 seconds is an acceptable
maximum for normal pages and most people can accept 15 seconds
response time for special functions such as searches and the recent
changes list.
The Polish Wikipedia has not a single sample above 15 seconds in these
24 hours. The majority of samples is in the lower two categories,
which is very good.
The Esperanto Wikipedia has a small number of samples above 15
seconds, which is sad but perhaps not alarming. The "recent changes"
has 56 % of its samples in the high 5-15 seconds response time
interval, which is a little high. Perhaps this could be fixed by
setting the default "recent changes" list from 7 or 3 days. Who can
change this setting? Tell me when you change, and I will report how
the response time changed. Almost all other samples are in the 0-2
and 2-5 categories, which is very good.
For the English Wikipedia, the static logotype image is served in less
than 2 seconds in 95 % of the samples. For this URL, there are no
samples in the 2-5 or 5-15 intervals, but a few samples have very long
response times. Perhaps the entire server was put on hold by some
other event? The last three lines of the report are depressing.
Almost none of the samples fall in the 0-2 or 2-5 categories. This
has to be analysed further by instrumenting the source code to report
where the delay is introduced.
I now have a running copy of the Wikipedia on my computer and have
started to experiment with this instrumentation. It's really straight
forward. In version 1.14 of wiki.phtml, Magnus Manske introduced the
function getmicrotime(), but the call to the function is commented
out. Just after getmicrotime(), I introduce a new function:
function trace($text){
global $startTime, $traceText;
$now = getmicrotime();
$elapsed = $now - $startTime;
if ($elapsed > 3.0) {
$traceText = "$traceText\nAfter $elapsed seconds: $text";
$startTime = $now;
}
}
Then at the beginning of the "main" program (where Magnus left a
commented-out first call to getmicrotime), I declare:
global $startTime, $traceText;
$startTime = getmicrotime();
$traceText = "";
Then at various points throughout the code, just after function calls
that I suspect are time bandits, I insert calls to my trace function:
trace("Just after updating the database");
These informative texts will accumulate in $traceText if the elapsed
time since the start is more than 3 seconds.
At the end of the "main" program comes the question, what should be
done with this $traceText? Should it be inserted into a new database
table? Or appended to the end of a text log file? Or inserted as an
HTML comment into the generated web page? Where can we best use this
information? The easiest but perhaps least useful is this:
trace("bottom of wiki.phtml main");
if ($traceText != "")
$out = "<!-- traceText:$traceText -->\n$out";
Who can implement this in the real source code? I'm not in the gang.
--
Lars Aronsson (lars@aronsson.se)
Aronsson Datateknik
Teknikringen 1e, SE-583 30 Linuxköping, Sweden
tel +46-70-7891609
http://aronsson.se/ http://elektrosmog.nu/ http://susning.nu/
Over the last 24 hours I've polled some URLs each 10 minutes and
measured the response time. This is a statistics report:
min avg max (count) <2 2-5 5-15 >15 URL - response times in seconds
0.75 2.00 11.79 ( 144) 68% 27% 4% 0% http://pl.wikipedia.com/wiki.cgi?Szwecja
0.56 2.70 89.78 ( 144) 95% 0% 0% 3% http://www.wikipedia.com/wiki.png
1.47 2.90 8.63 ( 144) 27% 64% 7% 0% http://pl.wikipedia.com/wiki.cgi?Ostatnie_zmiany
1.36 2.98 28.68 ( 144) 30% 62% 6% 0% http://pl.wikipedia.com/
0.83 3.21 91.86 ( 144) 94% 0% 0% 4% http://eo.wikipedia.com/vikio.png
1.00 4.45 140.53 ( 144) 63% 29% 2% 4% http://eo.wikipedia.com/wiki/Svedio
1.08 5.70 137.43 ( 144) 53% 34% 7% 4% http://eo.wikipedia.com/
3.40 7.09 68.23 ( 144) 0% 38% 56% 4% http://eo.wikipedia.com/wiki/Lastaj_Sxangxoj
3.35 13.59 203.39 ( 144) 0% 18% 63% 18% http://www.wikipedia.com/wiki/special:RecentChanges
1.61 28.38 411.43 ( 144) 4% 23% 33% 38% http://www.wikipedia.com/wiki/Sweden
3.86 45.16 359.17 ( 144) 0% 2% 38% 58% http://www.wikipedia.com/
The first three columns present the minimum, average, and maximum
response times. The rows are sorted on the average column. As you
can see the minimums are very good: 0.56 seconds roundtrip from Sweden
to San Diego is excellent. Even the English Wikipedia start page
(with the worst average in the list) has been served on 3.86 seconds,
which is quite good (this happened 6:10 am GMT). However, the
striking numbers are the maximum response times of several minutes.
The fourth column is the number of samples, which is 144 in 24 hours.
The following four columns present the statistical distribution of
samples in four categories: The percentage of samples that were less
than 2 seconds, those between 2 and 5 seconds, those between 5 and 15
seconds, and those in excess of 15 seconds. I thing usability gurus
like Jakob Nielsen has declared that 5 seconds is an acceptable
maximum for normal pages and most people can accept 15 seconds
response time for special functions such as searches and the recent
changes list.
The Polish Wikipedia has not a single sample above 15 seconds in these
24 hours. The majority of samples is in the lower two categories,
which is very good.
The Esperanto Wikipedia has a small number of samples above 15
seconds, which is sad but perhaps not alarming. The "recent changes"
has 56 % of its samples in the high 5-15 seconds response time
interval, which is a little high. Perhaps this could be fixed by
setting the default "recent changes" list from 7 or 3 days. Who can
change this setting? Tell me when you change, and I will report how
the response time changed. Almost all other samples are in the 0-2
and 2-5 categories, which is very good.
For the English Wikipedia, the static logotype image is served in less
than 2 seconds in 95 % of the samples. For this URL, there are no
samples in the 2-5 or 5-15 intervals, but a few samples have very long
response times. Perhaps the entire server was put on hold by some
other event? The last three lines of the report are depressing.
Almost none of the samples fall in the 0-2 or 2-5 categories. This
has to be analysed further by instrumenting the source code to report
where the delay is introduced.
I now have a running copy of the Wikipedia on my computer and have
started to experiment with this instrumentation. It's really straight
forward. In version 1.14 of wiki.phtml, Magnus Manske introduced the
function getmicrotime(), but the call to the function is commented
out. Just after getmicrotime(), I introduce a new function:
function trace($text){
global $startTime, $traceText;
$now = getmicrotime();
$elapsed = $now - $startTime;
if ($elapsed > 3.0) {
$traceText = "$traceText\nAfter $elapsed seconds: $text";
$startTime = $now;
}
}
Then at the beginning of the "main" program (where Magnus left a
commented-out first call to getmicrotime), I declare:
global $startTime, $traceText;
$startTime = getmicrotime();
$traceText = "";
Then at various points throughout the code, just after function calls
that I suspect are time bandits, I insert calls to my trace function:
trace("Just after updating the database");
These informative texts will accumulate in $traceText if the elapsed
time since the start is more than 3 seconds.
At the end of the "main" program comes the question, what should be
done with this $traceText? Should it be inserted into a new database
table? Or appended to the end of a text log file? Or inserted as an
HTML comment into the generated web page? Where can we best use this
information? The easiest but perhaps least useful is this:
trace("bottom of wiki.phtml main");
if ($traceText != "")
$out = "<!-- traceText:$traceText -->\n$out";
Who can implement this in the real source code? I'm not in the gang.
--
Lars Aronsson (lars@aronsson.se)
Aronsson Datateknik
Teknikringen 1e, SE-583 30 Linuxköping, Sweden
tel +46-70-7891609
http://aronsson.se/ http://elektrosmog.nu/ http://susning.nu/
