Add a read-mostly mode, in which entries won't share cache lines with
associated datas (probes, probe_bound, etc).
This makes write operations slower, but make get faster.
In ck_rhs_do_backward_shift_delete(), find if any entry with the same hash
is stored further, and if not, update probe_bound for every entry being
shifted, instead of just doing it for the slot being emptied.
This inefficiency was introduced in the overhaul of
the ck_epoch API.
Synchronize is executed with respect to e. At e + 1,
references can only exist to objects logically deleted
at e or e + 1. At e + 2, however, references can only exist to
objects logically deleted at e + 1 and e + 2. In the case that a
thread observes an out of date epoch value, an increment to the
global epoch would fail as the active bit is ordered with respect
to the memory barrier in synchronize. In the case that a protected
section begins after the memory barrier, then it is guaranteed
to not acquire the hazardous reference.
This does not change granularity of deferral lists, however.
There is still a requirement of 3 deferral lists on the fast path
(4 in ck_epoch for fast path purposes) as at any moment, any given
deferral list for value e can contain references to objects with
active references from both e and e - 1.
This operation is short-hand notation for rebuilding
a hash table. This rebuild can occur in the presence
of concurrent readers and will require twice the amount
of memory of the existing hash table until completion.
This borrows from a technique described by Purcell and Harris
in "Non-blocking hashtables with open addressing" technical report.
Essentially, every slot will have an associated local probe maxim,
including tombstones. Highly aggressive workloads may still require
occassional garbage collection.
This abstracts away pointer packing tricks to a macro,
fixes comparison of pointers to occur in absence of
embedded values and improves robustness of pointer marshaling
for write-side operations for pointers that may already have
had pointer packing tricks played on them.
Samy Al Bahra
Samy Al Bahra
Olivier Houchard
User Doginou