[PATCH] socket_helper: reduce constant lookups and caching

[Eric Wong <e@80x24.org>]

In Ruby 1.9.2+, socket options may be specified using symbols
instead of constants to avoid the need to import Socket::Constants
into the namespace.  This also has a nice side-effect of reducing
the size of the bytecode by trading 3 instructions (getinlinecache,
getconstant, setinlinecache) for one "putobject" instruction.

Nowadays, we may also avoid defining OS-specific constants ourselves
since 1.9+ versions of Ruby already provide them to further reduce
bytecode size.

getsockopt also returns Socket::Option objects in 1.9.2+,
allowing us to avoid the larger "unpack('i')" method dispatch
for an operand-free "int" method call.

Finally, favor Object#nil? calls rather than "== nil" comparisons
to reduce bytecode size even more.

Since this code is only called at startup time, it does not benefit
from inline caching of constant lookups in current mainline Ruby.

Combined, these changes reduce YARV bytecode size by around 2K on a
64-bit system.
---
 lib/unicorn/socket_helper.rb    | 78 +++++++++++++++--------------------------
 test/unit/test_socket_helper.rb |  2 +-
 2 files changed, 29 insertions(+), 51 deletions(-)

diff --git a/lib/unicorn/socket_helper.rb b/lib/unicorn/socket_helper.rb
index 820b778..2ecf438 100644
--- a/lib/unicorn/socket_helper.rb
+++ b/lib/unicorn/socket_helper.rb
@@ -4,8 +4,6 @@ require 'socket'
 
 module Unicorn
   module SocketHelper
-    # :stopdoc:
-    include Socket::Constants
 
     # prevents IO objects in here from being GC-ed
     # kill this when we drop 1.8 support
@@ -32,33 +30,11 @@ module Unicorn
       :tcp_nopush => nil,
       :tcp_nodelay => true,
     }
-    #:startdoc:
 
     # configure platform-specific options (only tested on Linux 2.6 so far)
-    case RUBY_PLATFORM
-    when /linux/
-      # from /usr/include/linux/tcp.h
-      TCP_DEFER_ACCEPT = 9 unless defined?(TCP_DEFER_ACCEPT)
-
-      # do not send out partial frames (Linux)
-      TCP_CORK = 3 unless defined?(TCP_CORK)
-
-      # Linux got SO_REUSEPORT in 3.9, BSDs have had it for ages
-      unless defined?(SO_REUSEPORT)
-        if RUBY_PLATFORM =~ /(?:alpha|mips|parisc|sparc)/
-          SO_REUSEPORT = 0x0200 # untested
-        else
-          SO_REUSEPORT = 15 # only tested on x86_64 and i686
-        end
-      end
-    when /freebsd/
-      # do not send out partial frames (FreeBSD)
-      TCP_NOPUSH = 4 unless defined?(TCP_NOPUSH)
-
-      def accf_arg(af_name)
-        [ af_name, nil ].pack('a16a240')
-      end if defined?(SO_ACCEPTFILTER)
-    end
+    def accf_arg(af_name)
+      [ af_name, nil ].pack('a16a240')
+    end if RUBY_PLATFORM =~ /freebsd/ && Socket.const_defined?(:SO_ACCEPTFILTER)
 
     def prevent_autoclose(io)
       if io.respond_to?(:autoclose=)
@@ -71,37 +47,38 @@ module Unicorn
     def set_tcp_sockopt(sock, opt)
       # just in case, even LANs can break sometimes.  Linux sysadmins
       # can lower net.ipv4.tcp_keepalive_* sysctl knobs to very low values.
-      sock.setsockopt(SOL_SOCKET, SO_KEEPALIVE, 1) if defined?(SO_KEEPALIVE)
+      Socket.const_defined?(:SO_KEEPALIVE) and
+        sock.setsockopt(:SOL_SOCKET, :SO_KEEPALIVE, 1)
 
-      if defined?(TCP_NODELAY)
+      if Socket.const_defined?(:TCP_NODELAY)
         val = opt[:tcp_nodelay]
-        val = DEFAULTS[:tcp_nodelay] if nil == val
-        sock.setsockopt(IPPROTO_TCP, TCP_NODELAY, val ? 1 : 0)
+        val = DEFAULTS[:tcp_nodelay] if val.nil?
+        sock.setsockopt(:IPPROTO_TCP, :TCP_NODELAY, val ? 1 : 0)
       end
 
       val = opt[:tcp_nopush]
       unless val.nil?
-        if defined?(TCP_CORK) # Linux
-          sock.setsockopt(IPPROTO_TCP, TCP_CORK, val)
-        elsif defined?(TCP_NOPUSH) # TCP_NOPUSH is lightly tested (FreeBSD)
-          sock.setsockopt(IPPROTO_TCP, TCP_NOPUSH, val)
+        if Socket.const_defined?(:TCP_CORK) # Linux
+          sock.setsockopt(:IPPROTO_TCP, :TCP_CORK, val)
+        elsif Socket.const_defined?(:TCP_NOPUSH) # FreeBSD
+          sock.setsockopt(:IPPROTO_TCP, :TCP_NOPUSH, val)
         end
       end
 
       # No good reason to ever have deferred accepts off
       # (except maybe benchmarking)
-      if defined?(TCP_DEFER_ACCEPT)
+      if Socket.const_defined?(:TCP_DEFER_ACCEPT)
         # this differs from nginx, since nginx doesn't allow us to
         # configure the the timeout...
         seconds = opt[:tcp_defer_accept]
         seconds = DEFAULTS[:tcp_defer_accept] if [true,nil].include?(seconds)
         seconds = 0 unless seconds # nil/false means disable this
-        sock.setsockopt(SOL_TCP, TCP_DEFER_ACCEPT, seconds)
+        sock.setsockopt(:IPPROTO_TCP, :TCP_DEFER_ACCEPT, seconds)
       elsif respond_to?(:accf_arg)
         name = opt[:accept_filter]
-        name = DEFAULTS[:accept_filter] if nil == name
+        name = DEFAULTS[:accept_filter] if name.nil?
         begin
-          sock.setsockopt(SOL_SOCKET, SO_ACCEPTFILTER, accf_arg(name))
+          sock.setsockopt(:SOL_SOCKET, :SO_ACCEPTFILTER, accf_arg(name))
         rescue => e
           logger.error("#{sock_name(sock)} " \
                        "failed to set accept_filter=#{name} (#{e.inspect})")
@@ -114,10 +91,11 @@ module Unicorn
 
       TCPSocket === sock and set_tcp_sockopt(sock, opt)
 
-      if opt[:rcvbuf] || opt[:sndbuf]
+      rcvbuf, sndbuf = opt.values_at(:rcvbuf, :sndbuf)
+      if rcvbuf || sndbuf
         log_buffer_sizes(sock, "before: ")
-        sock.setsockopt(SOL_SOCKET, SO_RCVBUF, opt[:rcvbuf]) if opt[:rcvbuf]
-        sock.setsockopt(SOL_SOCKET, SO_SNDBUF, opt[:sndbuf]) if opt[:sndbuf]
+        sock.setsockopt(:SOL_SOCKET, :SO_RCVBUF, rcvbuf) if rcvbuf
+        sock.setsockopt(:SOL_SOCKET, :SO_SNDBUF, sndbuf) if sndbuf
         log_buffer_sizes(sock, " after: ")
       end
       sock.listen(opt[:backlog])
@@ -126,8 +104,8 @@ module Unicorn
     end
 
     def log_buffer_sizes(sock, pfx = '')
-      rcvbuf = sock.getsockopt(SOL_SOCKET, SO_RCVBUF).unpack('i')
-      sndbuf = sock.getsockopt(SOL_SOCKET, SO_SNDBUF).unpack('i')
+      rcvbuf = sock.getsockopt(:SOL_SOCKET, :SO_RCVBUF).int
+      sndbuf = sock.getsockopt(:SOL_SOCKET, :SO_SNDBUF).int
       logger.info "#{pfx}#{sock_name(sock)} rcvbuf=#{rcvbuf} sndbuf=#{sndbuf}"
     end
 
@@ -172,15 +150,15 @@ module Unicorn
 
     def new_tcp_server(addr, port, opt)
       # n.b. we set FD_CLOEXEC in the workers
-      sock = Socket.new(opt[:ipv6] ? AF_INET6 : AF_INET, SOCK_STREAM, 0)
+      sock = Socket.new(opt[:ipv6] ? :AF_INET6 : :AF_INET, :SOCK_STREAM)
       if opt.key?(:ipv6only)
-        defined?(IPV6_V6ONLY) or
+        Socket.const_defined?(:IPV6_V6ONLY) or
           abort "Socket::IPV6_V6ONLY not defined, upgrade Ruby and/or your OS"
-        sock.setsockopt(IPPROTO_IPV6, IPV6_V6ONLY, opt[:ipv6only] ? 1 : 0)
+        sock.setsockopt(:IPPROTO_IPV6, :IPV6_V6ONLY, opt[:ipv6only] ? 1 : 0)
       end
-      sock.setsockopt(SOL_SOCKET, SO_REUSEADDR, 1)
-      if defined?(SO_REUSEPORT) && opt[:reuseport]
-        sock.setsockopt(SOL_SOCKET, SO_REUSEPORT, 1)
+      sock.setsockopt(:SOL_SOCKET, :SO_REUSEADDR, 1)
+      if Socket.const_defined?(:SO_REUSEPORT) && opt[:reuseport]
+        sock.setsockopt(:SOL_SOCKET, :SO_REUSEPORT, 1)
       end
       sock.bind(Socket.pack_sockaddr_in(port, addr))
       prevent_autoclose(sock)
diff --git a/test/unit/test_socket_helper.rb b/test/unit/test_socket_helper.rb
index 8992757..dd6881c 100644
--- a/test/unit/test_socket_helper.rb
+++ b/test/unit/test_socket_helper.rb
@@ -189,7 +189,7 @@ class TestSocketHelper < Test::Unit::TestCase
     port = unused_port @test_addr
     name = "#@test_addr:#{port}"
     sock = bind_listen(name, :reuseport => true)
-    cur = sock.getsockopt(Socket::SOL_SOCKET, SO_REUSEPORT).unpack('i')[0]
+    cur = sock.getsockopt(:SOL_SOCKET, :SO_REUSEPORT).int
     assert_operator cur, :>, 0
   rescue Errno::ENOPROTOOPT
     # kernel does not support SO_REUSEPORT (older Linux)
-- 
EW