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Under certain soft-stopping conditions (ie: sticktable attached to proxy and in-progress connections to the proxy that prevent haproxy from exiting), manage_proxy() (p->task) will wake up every second to perform a cleanup attempt on the proxy sticktable (to purge unused entries). However, as reported by TimWolla in GH #2091, it was found that a systematic call to pool_gc() could cause some CPU waste, mainly because malloc_trim() (which is rather expensive) is being called for each pool_gc() invocation. As a result, such soft-stopping process could be spending a significant amount of time in the malloc_trim->madvise() syscall for nothing. Example "strace -c -f -p `pidof haproxy`" output (taken from Tim's report): % time seconds usecs/call calls errors syscall ------ ----------- ----------- --------- --------- ---------------- 46.77 1.840549 3941 467 1 epoll_wait 43.82 1.724708 13 128509 sched_yield 8.82 0.346968 11 29696 madvise 0.58 0.023011 24 951 clock_gettime 0.01 0.000257 10 25 7 recvfrom 0.00 0.000033 11 3 sendto 0.00 0.000021 21 1 rt_sigreturn 0.00 0.000021 21 1 timer_settime ------ ----------- ----------- --------- --------- ---------------- 100.00 3.935568 24 159653 8 total To prevent this, we now only call pool_gc() when some memory is really expected to be reclaimed as a direct result of the previous stick table cleanup. This is pretty straightforward since stktable_trash_oldest() returns the number of trashed sticky sessions. This may be backported to every stable versions.
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)