Luke Melia <[email protected]> wrote:
> I've been analyzing our Unicorn-powered Rails app's performance, and
> have found that garbage collection is a big factor in slow requests.
>
> In the interest of avoiding those performance hits while handling
> requests, would it be possible to have a unicorn worker run garbage
> collection after handling a request and before waiting for the next
> one? Would this be a good idea?
Hi Luke,
I made this for one heavyweight app a while back.
I guess I should throw this into the examples section, but it won't be
the default since it hurts simpler applications that don't generate
much garbage.
==> big_app_gc.rb <==
# This shouldn't hurt overall performance as long as the server cluster
# is at <=50% CPU capacity, and improves the performance of most memory
# intensive requests. This serves to improve _client-visible_
# performance (possibly at the cost of overall performance).
#
# We'll call GC after each request is been written out to the socket, so
# the client never sees the extra GC hit it. It's ideal to call the GC
# inside the HTTP server (vs middleware or hooks) since the stack is
# smaller at this point, so the GC will both be faster and more
# effective at releasing unused memory.
#
# This monkey patch is _only_ effective for applications that use a lot
# of memory, and will hurt simpler apps/endpoints that can process
# multiple requests before incurring GC.
class Unicorn::HttpServer
REQ = Unicorn::HttpRequest::REQ
alias _process_client process_client
undef_method :process_client
def process_client(client)
_process_client(client)
REQ.clear
GC.start
end
end if defined?(Unicorn)
--
Eric Wong
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