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Some of the recent optimizations around the polling to save a few epoll_ctl() calls have shown that they could also cause some trouble. However, over time our code base has become totally asynchronous with I/Os always attempted from the upper layers and only retried at the bottom, making it look like we're getting closer to EPOLLET support. There are showstoppers there such as the listeners which cannot support this. But given that most of the epoll_ctl() dance comes from the connections, we can try to enable edge-triggered polling on connections. What this patch does is to add a new global tunable "tune.fd.edge-triggered", that makes fd_insert() automatically set an et_possible bit on the fd if the I/O callback is conn_fd_handler. When the epoll code sees an update for such an FD, it immediately registers it in both directions the first time and doesn't update it anymore. On a few tests it proved quite useful with a 14% request rate increase in a H2->H1 scenario, reducing the epoll_ctl() calls from 2 per request to 2 per connection. The option is obviously disabled by default as bugs are still expected, particularly around the subscribe() code where it is possible that some layers do not always re-attempt reading data after being woken up.
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)