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231d3d32be
Based on Willy's idea (from 3.0-dev6 announcement message): in this patch we try to reduce the max latency that can be caused by running lua scripts with default settings. Indeed, by default, hlua engine is allowed to process up to 10k instructions per batch. While this value was found to be the optimal one for a single thread, it turns out that keeping a thread busy for 10k lua instructions could increase thread contention. This is especially true when the script is loaded with 'lua-load', because in that case the current thread owns the main lua lock and prevent other threads from making any progress if they're also waiting on the main lock. Thanks to Thierry Fournier's work, we know that performance-wise we can reach optimal performance by sticking between 500 and 10k instructions per batch. Given that, when the script is loaded using 'lua-load', if no "tune.lua.forced-yield" was set by the user, we automatically divide the default value (10K) by the number of threads haproxy can use to reduce thread contention (given that all threads could compete for the main lua lock), however we make sure not to return a value below 500, because Thierry's work showed that this would come with a significant performance loss. The historical behavior may still be enforced by setting "tune.lua.forced-yield" to 10000 in the global config section.