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Due to the ts->ref_cnt being manipulated and checked inside wrlocks,
we continue to have it updated under plenty of read locks, which have
an important cost on many-thread machines.
This patch turns them all to atomic ops and carefully moves them outside
of locks every time this is possible:
- the ref_cnt is incremented before write-unlocking on creation otherwise
the element could vanish before we can do it
- the ref_cnt is decremented after write-locking on release
- for all other cases it's updated out of locks since it's guaranteed by
the sequence that it cannot vanish
- checks are done before locking every time it's used to decide
whether we're going to release the element (saves several write locks)
- expiration tests are just done using atomic loads, since there's no
particular ordering constraint there, we just want consistent values.
For Lua, the loop that is used to dump stick-tables could switch to read
locks only, but this was not done.
For peers, the loop that builds updates in peer_send_teachmsgs is extremely
expensive in write locks and it doesn't seem this is really needed since
the only updated variables are last_pushed and commitupdate, the first
one being on the shared table (thus not used by other threads) and the
commitupdate could likely be changed using a CAS. Thus all of this could
theoretically move under a read lock, but that was not done here.
On a 80-thread machine with a peers section enabled, the request rate
increased from 415 to 520k rps.
The HAProxy documentation has been split into a number of different files for ease of use. Please refer to the following files depending on what you're looking for : - INSTALL for instructions on how to build and install HAProxy - BRANCHES to understand the project's life cycle and what version to use - LICENSE for the project's license - CONTRIBUTING for the process to follow to submit contributions The more detailed documentation is located into the doc/ directory : - doc/intro.txt for a quick introduction on HAProxy - doc/configuration.txt for the configuration's reference manual - doc/lua.txt for the Lua's reference manual - doc/SPOE.txt for how to use the SPOE engine - doc/network-namespaces.txt for how to use network namespaces under Linux - doc/management.txt for the management guide - doc/regression-testing.txt for how to use the regression testing suite - doc/peers.txt for the peers protocol reference - doc/coding-style.txt for how to adopt HAProxy's coding style - doc/internals for developer-specific documentation (not all up to date)