What I understand by "pre-forking daemon" (or more usually, "pre-forking server") is a process with a dynamic number of forked children which manages the child pool so that there are always some idle children waiting for client requests. This is done as a compromise to improve latency without committing vast amounts of memory. If there were a set number of children (say 64) then you might have a situation where all 64 of them are sitting around doing nothing just waiting for a request and hogging memory while it happens. OTOH, if you only fork a child when a request comes in the heavy act of forking introduces latency in the response. By having a stipulated, configurable range of "spare" children you get the best of both worlds. That's the theory, anyway.

Apache 1.x used this method and you can still run Apache 2.x this way if you choose (but most use a threaded MPM instead). PHP-FPM seems to use a similar mechanism as do some nameservers, etc.

In reply to Re^2: Pre-Forking Daemon with Parallel::ForkManager by hippo
in thread Pre-Forking Daemon with Parallel::ForkManager by enemyofthestate

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • 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:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, 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, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.