nginx + lua and GC latency

Dirk Feytons dirk.feytons at
Mon Dec 10 09:00:34 UTC 2012

Are you talking about ?
>From what I've heard about ngx_lua people are using it in large production
environments and I haven't heard them complain about GC pauses (at least
not publicly on the mailing list). But that doesn't mean that Mike is
wrong. The Lua GC is known to not scale that well when the number of
objects increases. Whether you hit those limits can only be determined by
actually trying :)

Dirk F.

On Sat, Dec 8, 2012 at 10:25 PM, Dave Bailey <dave at> wrote:

> Hi,
> I am thinking of embedding Lua into nginx for some things where I need a
> little more flexibility than my current module implementations allow.
> Before I invest the time into this, I was wondering if any of you have
> looked into the LuaJit GC latency.  Mike Pall has a wiki page outlining his
> plans for a new GC in LuaJIT 3.0:
> It sounds like he is not too thrilled with the performance of the current
> (2.0) LuaJit GC, but I don't know if this means it's something I would need
> to worry about, or if the latency of the current GC is fine.  Has anyone
> done any profiling to measure this on nginx under "real" load (e.g. 1k-2k
> req/s and 100-200+ Mbits/s bandwidth per worker, or somewhere in that
> range)?  I like the flexibility that embedding LuaJit would give me, but
> can't really afford GC pauses unless I know the latency is going to stay
> below some reasonable value (maybe in the realm of 100 microseconds).
> I am mainly interested in relatively simple Lua operations for now, such
> as customized URL routing and other things that one could expect to be done
> once per request.  Any info would be much appreciated.  Thanks-
> -dave
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