Tony Finch 4b5ec07bb7 Refactor qp-trie to use QSBR ... The first working multi-threaded qp-trie was stuck with an unpleasant trade-off: * Use `isc_rwlock`, which has acceptable write performance, but terrible read scalability because the qp-trie made all accesses through a single lock. * Use `liburcu`, which has great read scalability, but terrible write performance, because I was relying on `rcu_synchronize()` which is rather slow. And `liburcu` is LGPL. To get the best of both worlds, we need our own scalable read side, which we now have with `isc_qsbr`. And we need to modify the write side so that it is not blocked by readers. Better write performance requires an async cleanup function like `call_rcu()`, instead of the blocking `rcu_synchronize()`. (There is no blocking cleanup in `isc_qsbr`, because I have concluded that it would be an attractive nuisance.) Until now, all my multithreading qp-trie designs have been based around two versions, read-only and mutable. This is too few to work with asynchronous cleanup. The bare minimum (as in epoch based reclamation) is three, but it makes more sense to support an arbitrary number. Doing multi-version support "properly" makes fewer assumptions about how safe memory reclamation works, and it makes snapshots and rollbacks simpler. To avoid making the memory management even more complicated, I have introduced a new kind of "packed reader node" to anchor the root of a version of the trie. This is simpler because it re-uses the existing chunk lifetime logic - see the discussion under "packed reader nodes" in `qp_p.h`. I have also made the chunk lifetime logic simpler. The idea of a "generation" is gone; instead, chunks are either mutable or immutable. And the QSBR phase number is used to indicate when a chunk can be reclaimed. Instead of the `shared_base` flag (which was basically a one-bit reference count, with a two version limit) the base array now has a refcount, which replaces the confusing ad-hoc lifetime logic with something more familiar and systematic.		2023-02-27 13:47:55 +00:00
..
addressdb	Update the copyright information in all files in the repository	2022-01-11 09:05:02 +01:00
cds-child	Update the copyright information in all files in the repository	2022-01-11 09:05:02 +01:00
database	Update the copyright information in all files in the repository	2022-01-11 09:05:02 +01:00
db_rules	Update the copyright information in all files in the repository	2022-01-11 09:05:02 +01:00
dispatch	Update the copyright information in all files in the repository	2022-01-11 09:05:02 +01:00
dnssec-policy	Update the copyright information in all files in the repository	2022-01-11 09:05:02 +01:00
ncache	Update the copyright information in all files in the repository	2022-01-11 09:05:02 +01:00
netmgr.md	Update the copyright information in all files in the repository	2022-01-11 09:05:02 +01:00
qp-trie.md	Refactor qp-trie to use QSBR	2023-02-27 13:47:55 +00:00
rdataset	Update the copyright information in all files in the repository	2022-01-11 09:05:02 +01:00
red-black	Update the copyright information in all files in the repository	2022-01-11 09:05:02 +01:00
resolver	Update the copyright information in all files in the repository	2022-01-11 09:05:02 +01:00
search	Update the copyright information in all files in the repository	2022-01-11 09:05:02 +01:00
tasks	Remove isc_task_destroy() and isc_task_shutdown()	2022-05-12 14:55:49 +02:00
unsupported-algorithms-in-bind9	Update the copyright information in all files in the repository	2022-01-11 09:05:02 +01:00
verify	Update the copyright information in all files in the repository	2022-01-11 09:05:02 +01:00
zone	Update netmgr, tasks, and applications to use isc_loopmgr	2022-08-26 09:09:24 +02:00