From: Alessio Podda <alessio@isc.org>
Date: Wed, 9 Jul 2025 14:17:02 +0000 (+0000)
Subject: chg: dev: Replace per-zone lock buckets with global buckets
X-Git-Tag: v9.21.11~59
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e0d1d936de8f6de43b4df916cae10331731a3f19;p=thirdparty%2Fbind9.git

chg: dev: Replace per-zone lock buckets with global buckets

Qpzone employs a locking strategy where rwlocks are grouped into
buckets, and each zone gets 17 buckets.
This strategy is suboptimal in two ways:
 - If named is serving a single zone or a zone is the majority of the
   traffic, this strategy pretty much guarantees contention when using
   more than a dozen threads.
 - If named is serving many small zones, it causes substantial memory
   usage.

This commit switches the locking to a global table initialized at start
time. This should have three effects:
 - Performance should improve in the single zone case, since now we are
   selecting from a bigger pool of locks.
 - Memory consumption should go down significantly in the many zone
   cases.
 - Performance should not degrade substantially in the many zone cases.
   The reason for this is that, while we could have substantially more
   zones than locks, we can query/edit only O(num threads) at the same
   time. So by making the global table much bigger than the expected
   number of threads, we can limit contention.

Merge branch 'alessio/global-qpzone-lock-table' into 'main'

See merge request isc-projects/bind9!10446
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e0d1d936de8f6de43b4df916cae10331731a3f19