tree 2016c1fee5864bf7d8ab27b213da97e6dad47d2f
parent 7a798e5d6b2f7134db34028f5052a9865ca9d946
author Willy Tarreau <w@1wt.eu> 1460627258 +0200
committer Willy Tarreau <w@1wt.eu> 1460627630 +0200
encoding latin1

BUG/MEDIUM: fix maxaccept computation on per-process listeners

Christian Ruppert reported a performance degradation when binding a
single frontend to many processes while only one bind line was being
used, bound to a single process.

The reason comes from the fact that whenever a listener is bound to
multiple processes, the it is assigned a maxaccept value which equals
half the global maxaccept value divided by the number of processes the
frontend is bound to. The purpose is to ensure that no single process
will drain all the incoming requests at once and ensure a fair share
between all listeners. Usually this works pretty well, when a listener
is bound to all the processes of its frontend. But here we're in a
situation where the maxaccept of a listener which is bound to a single
process is still divided by a large value.

The fix consists in taking into account the number of processes the
listener is bound do and not only those of the frontend. This way it
is perfectly possible to benefit from nbproc and SO_REUSEPORT without
performance degradation.

1.6 and 1.5 normally suffer from the same issue.