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author | Eric Wong <e@80x24.org> | 2016-11-28 23:50:10 +0000 |
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committer | Eric Wong <e@80x24.org> | 2016-11-28 23:50:10 +0000 |
commit | d89381efe5b6f4d1233aba16907bb457ff5f1f13 (patch) | |
tree | 914286b69d47182359f52ca5adc0ed208af14e9a | |
parent | 0383705344aa45970f0f799078a9b138202a8c6f (diff) | |
download | unicorn-d89381efe5b6f4d1233aba16907bb457ff5f1f13.tar.gz |
This probably applies to other kernels, too, but I'm most familiar with Linux.
-rw-r--r-- | TUNING | 20 |
1 files changed, 19 insertions, 1 deletions
@@ -72,10 +72,28 @@ See Unicorn::Configurator for details on the config file format. have them unbuffered (File#sync = true) or they are record(line)-buffered in userspace before any writes. -== Kernel Parameters (Linux sysctl) +== Kernel Parameters (Linux sysctl and sysfs) WARNING: Do not change system parameters unless you know what you're doing! +* Transparent hugepages (THP) improves performance in many cases, + but can also increase memory use when relying on a + copy-on-write(CoW)-friendly GC (Ruby 2.0+) with "preload_app true". + CoW operates at the page level, so writing to a huge page would + trigger a 2 MB copy (x86-64), as opposed to a 4 KB copy on a + regular (non-huge) page. + + Consider only allowing THP to be used when it is requested via the + madvise(2) syscall: + + echo madvise >/sys/kernel/mm/transparent_hugepage/enabled + + Or disabling it system-wide, via "never". + + n.b. "page" in this context only applies to the OS kernel, + Ruby GC implementations also use this term for the same concept + in a way that is agnostic to the OS. + * net.core.rmem_max and net.core.wmem_max can increase the allowed size of :rcvbuf and :sndbuf respectively. This is mostly only useful for UNIX domain sockets which do not have auto-tuning buffer sizes. |