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HAProxy - Load balancer
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Willy Tarreau 8da18bfa29 MEDIUM: tools: switch the main PRNG to a thread-local xoshiro256** 
The current PRNG is xoroshiro128**, it was introduced in 2.2 with
commit 52bf83939 ("BUG/MEDIUM: random: implement a thread-safe and
process-safe PRNG").  It features a 2^128 sequence and can perform
2^64 or 2^96 jumps, though only the 2^96 jump is implemented. It
was initially designed to support both processes and threads, and
implements a shared state between threads instead of allocating
distinct sequences based on PID and thread numbers.

Since then, the PRNG's usage grew and processes have disappeared,
but the lock or the DWCAS are still there due to its shared nature.

Also, UUID and QUIC retry tokens now consume 128 bits from the PRNG
in two 64-bit calls, and used to weaken the PRNG by rapidly disclosing
its internal state on reasonably idle systems. This indicates that
most of the time we now need 128 bits.

This patch modernizes the internal generator by switching to xoshiro256**,
which has comparable properties (it's even faster), and features even
longer 2^256 periods, still returning 64 bits per call. It can be
initialized with 2^128 and 2^192 jumps. More details here:

   https://prng.di.unimi.it/
   https://prng.di.unimi.it/xoshiro256starstar.c

Here we implement a thread-local state instead of the old shared one,
so there is no more need for synchronization. The state is seeded at
boot, and each thread performs as many 2^192 jumps as their TID is
large. The master process performs a 2^128 jump where it used to
perform a 2^96 jump so that it doesn't overlap with any worker thread.
However a cleaner approach could be to perform a 2^128 jump for each
fork() (here the worker) and 2^192 for each thread. This might be for
a future improvement.

ha_random64_internal() is now the new PRNG, so that everything else
remains totally transparent. _ha_random64_pair_hashed() continues to
hash the first 128 bits of the state.

A simple config generating 100 UUID on 20 threads jumps from 135k to
1.25M req/s, which translates to a bump from 13.5M to 125M UUID/s,
or 9 times faster. And there is no more DWCAS can be seen anymore
in perf top:

Before:
Overhead  Shared Object            Symbol
  99.04%  haproxy       [.] ha_random64_internal
   0.66%  haproxy       [.] _ha_random64_pair_hashed
   0.03%  libc-2.42.so  [.] __printf_buffer
   0.02%  [kernel]      [k] _raw_spin_lock
   0.01%  libc-2.42.so  [.] __strchrnul_avx2
   0.01%  [kernel]      [k] ktime_get
   0.01%  [kernel]      [k] lapic_next_deadline
   0.01%  haproxy       [.] sample_process
   0.01%  haproxy       [.] chunk_printf
   0.01%  libc-2.42.so  [.] __printf_buffer_write
   0.01%  [kernel]      [k] hrtimer_active
   0.01%  libc-2.42.so  [.] __memmove_avx_unaligned_erms
   0.01%  libc-2.42.so  [.] _itoa_word

After:
  18.84%  libc-2.42.so      [.] __printf_buffer
   9.84%  haproxy           [.] sample_process
   8.33%  libc-2.42.so      [.] __strchrnul_avx2
   6.61%  libc-2.42.so      [.] __memmove_avx_unaligned_erms
   6.06%  libc-2.42.so      [.] __printf_buffer_write
   4.43%  haproxy           [.] strlcpy2
   4.09%  libc-2.42.so      [.] _itoa_word
   2.62%  haproxy           [.] sess_build_logline_orig
   2.12%  haproxy           [.] _ha_random64_pair_hashed
   1.28%  haproxy           [.] pool_put_to_cache
   1.06%  haproxy           [.] __pool_alloc
   1.00%  haproxy           [.] smp_fetch_uuid
   0.93%  haproxy           [.] lf_text_len
   0.82%  haproxy           [.] ha_generate_uuid_v4
2026-05-25 20:50:18 +02:00
.github CI: github: add DEBUG_STRICT=2 to ASAN jobs 2026-04-30 17:46:30 +02:00
addons BUILD: 51d.c: cleanup, fix preprocessor ifdefs 2026-05-13 17:00:20 +02:00
admin CLEANUP: fix typos and spelling in comments and documentation 2026-03-30 09:24:19 +02:00
dev CLEANUP: fix typos and spelling in comments and documentation 2026-03-30 09:24:19 +02:00
doc MINOR: config: shm-stats-file is no longer experimental 2026-05-21 08:50:20 +02:00
examples MEDIUM: mux_quic: rename qmux traces to qcm 2026-05-13 16:23:58 +02:00
include MEDIUM: tools: switch the main PRNG to a thread-local xoshiro256** 2026-05-25 20:50:18 +02:00
reg-tests BUG/MINOR: h1: Don't mask websocket protocol if multiple protocols used 2026-05-19 17:50:50 +02:00
scripts SCRIPTS: announce-release: add a link to the OpenTelemetry filter 2026-05-08 12:05:09 +02:00
src MEDIUM: tools: switch the main PRNG to a thread-local xoshiro256** 2026-05-25 20:50:18 +02:00
tests TESTS: quic: add unit-tests for QUIC TX part 2025-09-08 14:49:03 +02:00
.cirrus.yml CI: cirrus-ci: bump FreeBSD image to 14-3 2025-10-09 14:06:48 +02:00
.gitattributes MINOR: Configure the cpp userdiff driver for *.[ch] in .gitattributes 2021-02-22 18:17:57 +01:00
.gitignore MINOR: tevt/dev: Add term_events tool 2025-01-31 10:41:50 +01:00
.mailmap DOC: update Tim's address in .mailmap 2021-09-16 09:14:14 +02:00
.travis.yml MEDIUM: mworker: remove USE_SYSTEMD requirement for -Ws 2024-11-20 12:07:38 +01:00
BRANCHES CLEANUP: tree-wide: fix typos in user-invisible files 2026-05-13 17:03:48 +02:00
BSDmakefile BUILD: makefile: commit the tiny FreeBSD makefile stub 2023-05-24 17:17:36 +02:00
CHANGELOG [RELEASE] Released version 3.4-dev13 2026-05-20 17:46:36 +02:00
CONTRIBUTING CLEANUP: assorted typo fixes in the code and comments 2025-04-02 11:12:20 +02:00
INSTALL DOC: update supported gcc and openssl versions in INSTALL 2026-05-20 17:45:23 +02:00
LICENSE LICENSE: add licence exception for OpenSSL 2012-09-07 13:52:26 +02:00
MAINTAINERS MAJOR: spoe: Let the SPOE back into the game 2024-05-22 09:04:38 +02:00
Makefile BUILD: traces: add USE_TRACE allowing to disable traces 2026-05-20 11:46:43 +02:00
README.md CI: github: add cross-zoo.yml in README.md 2026-04-20 11:47:20 +02:00
SUBVERS BUILD: use format tags in VERDATE and SUBVERS files 2013-12-10 11:22:49 +01:00
VERDATE [RELEASE] Released version 3.4-dev13 2026-05-20 17:46:36 +02:00
VERSION [RELEASE] Released version 3.4-dev13 2026-05-20 17:46:36 +02:00

README.md

HAProxy

AWS-LC Illumos NetBSD CrossCompile FreeBSD VTest

HAProxy logo

HAProxy is a free, very fast and reliable reverse-proxy offering high availability, load balancing, and proxying for TCP and HTTP-based applications.

Installation

The INSTALL file describes how to build HAProxy. A list of packages is also available on the wiki.

Getting help

The discourse and the mailing-list are available for questions or configuration assistance. You can also use the slack or IRC channel. Please don't use the issue tracker for these.

The issue tracker is only for bug reports or feature requests.

Documentation

The HAProxy documentation has been split into a number of different files for ease of use. It is available in text format as well as HTML. The wiki is also meant to replace the old architecture guide.

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:

License

HAProxy is licensed under GPL 2 or any later version, the headers under LGPL 2.1. See the LICENSE file for a more detailed explanation.