alarm works without active waiting,
Since the advent of SAFE_SIGNALS; alarm won't interrupt long running opcodes.
And the cpu requirement of the "active waiting" -- waking 1 per second:
C:\test>perl -E"sleep 1 for 1..120; say join ' ', times"
0 0.015 0 0
0.015/120 = 0.0125% cpu usage; means that it would require 8000 of these actively waiting tasks to even register a blip on a cpu usage graph.
sleep 1 does not always sleep exactly one second.
On modern OSs, the differences are tiny -- essentially the time taken between the 1 second elapsing and the process getting its next time-slice:
C:\test>perl -MTime::HiRes=time -E"$t=time; sleep 1 for 1 .. 10*60; pr
+int (time()-$t) - 10*60"
601.386687040329 - 600 / 600 = 0.002311145067215. A couple of milliseconds
Which means that after 10 minutes of waiting, those tiny differences will have accumulated such that you've ended up giving the user a whole extra second in which to respond. Big deal.
But the kicker is: alarm will suffer from the essentially the same delays and inaccuracies! Once the system timer times out and sets the flag in the kernel thread structure; it still won't run until it filters its way to the top of the schedulers list of run-eligible threads.
Re-reading the post to which you responded and the OP; the former is almost certainly not a solution to the latter -- but definitely not because of the reasons you cite. They are just sweating the small stuff whilst ignoring the bigger picture.
With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.
Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
Read Where should I post X? if you're not absolutely sure you're posting in the right place.
Please read these before you post! —
Posts may use any of the Perl Monks Approved HTML tags:
You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
- a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
Link using PerlMonks shortcuts! What shortcuts can I use for linking?
See Writeup Formatting Tips and other pages linked from there for more info.
| & || & |
| < || < |
| > || > |
| [ || [ |
| ] || ] ||