Tony Finch 9b7aa536ba QSBR: safe memory reclamation for lock-free data structures ... This "quiescent state based reclamation" module provides support for the qp-trie module in dns/qp. It is a replacement for liburcu, written without reference to the urcu source code, and in fact it works in a significantly different way. A few specifics of BIND make this variant of QSBR somewhat simpler: * We can require that wait-free access to a qp-trie only happens in an isc_loop callback. The loop provides a natural quiescent state, after the callbacks are done, when no qp-trie access occurs. * We can dispense with any API like rcu_synchronize(). In practice, it takes far too long to wait for a grace period to elapse for each write to a data structure. * We use the idea of "phases" (aka epochs or eras) from EBR to reduce the amount of bookkeeping needed to track memory that is no longer needed, knowing that the qp-trie does most of that work already. I considered hazard pointers for safe memory reclamation. They have more read-side overhead (updating the hazard pointers) and it wasn't clear to me how to nicely schedule the cleanup work. Another alternative, epoch-based reclamation, is designed for fine-grained lock-free updates, so it needs some rethinking to work well with the heavily read-biased design of the qp-trie. QSBR has the fastest read side of the basic SMR algorithms (with no barriers), and fits well into a libuv loop. More recent hybrid SMR algorithms do not appear to have enough benefits to justify the extra complexity.		2023-02-23 15:57:53 +00:00
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copyrights	Update the copyright information in all files in the repository	2022-01-11 09:05:02 +01:00
dev.md	Simple lock-free stack in <isc/stack.h>	2023-02-22 16:13:37 +00:00
HOW-ADB-WORKS.txt	Update the copyright information in all files in the repository	2022-01-11 09:05:02 +01:00
libuv.md	Add developer note for the libuv quirks	2022-09-19 14:38:56 +02:00
loopmgr.md	remove references to obsolete isc_task/timer functions	2023-02-22 08:13:30 +00:00
qsbr.md	QSBR: safe memory reclamation for lock-free data structures	2023-02-23 15:57:53 +00:00
rdata.md	Shrink decompression contexts	2022-06-01 13:00:40 +01:00
results	remove references to obsolete isc_task/timer functions	2023-02-22 08:13:30 +00:00
style.md	remove references to obsolete isc_task/timer functions	2023-02-22 08:13:30 +00:00
unexpected	De-duplicate __FILE__, __LINE__	2022-10-17 11:58:26 +01:00