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A test on large objects revealed a big performance loss from 2.1. The cause was found to be related to cache locality between scheduled operations that are batched using tasklets. It happens that we now have several layers of tasklets and that queuing all these operations leaves time to let memory objects cool down in the CPU cache, effectively resulting in halving the performance. A quick test consisting in putting most unknown tasklets into the BULK queue almost fixed the performance regression, but this is a wrong approach as it can also slow down some low-latency transfers or access to applets like the CLI. What this patch does instead is to queue unknown tasklets into the same queue as the current one when tasklet_wakeup() is itself called from a task/tasklet, otherwise it uses urgent for real I/O (when sched->current is NULL). This results in the called tasklet being woken up much sooner, often at the end of the current batch of tasklets. By doing so, a test on 2 cores 4 threads with 256 concurrent H1 conns transferring 16m objects with 256kB buffers jumped from 55 to 88 Gbps. It's even possible to go as high as 101 Gbps by evaluating the URGENT queue after the BULK one, though this was not done as considered dangerous for latency sensitive operations. This reinforces the importance of getting back the CPU transfer mechanisms based on tasklet_wakeup_after() to work at the tasklet level by supporting an immediate wakeup in certain cases. No backport is needed, this is strictly 2.2. |
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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)