Check timings

[heikkilevanto]

Add some code to see what takes all the time. I suspect the worst offenders are

• Fetching a beer board
• Invoking gnuplot
• Possibly reading the file
• creating the plot command and plot data file file for gnuplot

But don't trust intuition on performance questions. Measure it. There is a good Perl module for such: Time::HiRes

Add code to measure the key points, and log them into stderr and/or html comments.

[heikkilevanto]

Just looking at the browser console, running at home on the same machine

• about page takes a bit over 500 ms, since it too reads the data file.
• The full list, even with graph and beer board don't take 600ms.
• The full list for 2023, with 1457 entries (the most I have), takes some 800 ms.
• The various lists (beer etc) take a bit more, but usually under a second
• The monthly stats takes some 800 ms, as do the other stats

Would be good to see what Perl can say about the total time spent in the script. Apaches overhead seems to be about 2 ms (reloading the icon)

[heikkilevanto]

Reading the whole file, but parsing only lines for 2024 drops the time from 700 to under 150 ms. So it is the parsing, not reading through the file that costs. Most of the time we don't need to parse all records.

See also #257