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There's a risk that fdtab is not 64-byte aligned. The first effect is that it may cause false sharing between cache lines resulting in contention when adjacent FDs are used by different threads. The second is related to what is explained in commit "BUG/MAJOR: compiler: relax alignment constraints on certain structures", i.e. that modern compilers might make use of aligned vector operations to zero some entries, and would crash. We do not use any memset() or so on fdtab, so the risk is almost inexistent, but that's not a reason for violating some valid assumptions. This patch addresses this by allocating 64 extra bytes and aligning the structure manually (this is an extremely cheap solution for this specific case). The original address is stored in a new variable "fdtab_addr" and is the one that gets freed. This remains extremely simple and should be easily backportable. A dedicated aligned allocator later would help, of course. This needs to be backported as far as 2.2. No issue related to this was reported yet, but it could very well happen as compilers evolve. In addition this should preserve high performance across restarts (i.e. no more dependency on allocator's alignment). |
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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)