Add a note in ThreadsPerChild about the relationship with ThreadsLimit.

    <p>A <var>ratio</var> between the number of (online) CPU cores and the

    number of listeners' buckets can be used to make Apache HTTP Server create

    <code>num_cpu_cores / ratio</code> listening buckets, each containing its

    own <directive>Listen</directive>-ing socket(s) on the same port(s), and

    own <directive module="mpm_common">Listen</directive>-ing socket(s) on the same port(s), and

    then make each child handle a single bucket (with round-robin distribution

    of the buckets at children creation time).</p>

    <p>The default value for <directive>ThreadsPerChild</directive> is

    <code>64</code> when used with <module>mpm_winnt</module> and

    <code>25</code> when used with the others.</p>

    <p>The value of <directive>ThreadsPerChild</directive> can not exceed the

    value of <directive module="mpm_common">ThreadsLimit</directive>. If a

    higher value is configured, it will be automatically reduced at start-up

    and a warning will be logged. The relationship between these 2 directives

    is explained in <directive module="mpm_common">ThreadsLimit</directive>.</p>

</usage>

</directivesynopsis>