net/http: use writev for HTTP chunked request bodies

This reduces both user and system CPU time for large
uploads with dynamically-generated request bodies.

              user     system      total        real
before:   0.393334   1.580000   1.973334 (  1.971066)
after:    0.223334   0.976666   1.200000 (  1.198514)

------
require 'socket'
require 'net/http'
require 'benchmark'
nr = 1024 * 1024 * 1024
s = TCPServer.new('127.0.0.1', 0)
addr = s.addr
at_exit { Process.waitall }
fork do
  c = s.accept
  # not exactly accurate but fast
  IO.copy_stream(c, '/dev/null', nr + 500000)
  begin
    buf = c.readpartial(16384)
    tmp = ''
    until buf.end_with?(-"0\r\n\r\n")
      buf << c.readpartial(16384, tmp)
    end
  rescue EOFError
  end
  c.write "HTTP/1.1 201 Created\r\nConnection:close\r\n\r\n"
  c.close
end
r, w = IO.pipe
fork do
  r.close
  IO.copy_stream('/dev/zero', w, nr)
  w.close
end
w.close
Net::HTTP.start(addr[3], addr[1]) do |http|
  put = Net::HTTP::Put.new('/dev0/foo')
  put['Content-Type'] = 'application/content-type'
  put['Transfer-Encoding'] = 'chunked'
  put.body_stream = r
  puts(Benchmark.measure { http.request(put) })
end
------

* lib/net/http/generic_request.rb (write): use multi-arg write
* lib/net/protocol.rb (write): support multi-arg
  (write0): ditto
  [ruby-core:84845] [Feature #14339]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@61812 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/net/http/generic_request.rb

@@ -168,9 +168,8 @@ class Net::HTTPGenericRequest
 
     def write(buf)
       # avoid memcpy() of buf, buf can huge and eat memory bandwidth
-      @sock.write("#{buf.bytesize.to_s(16)}\r\n")
-      rv = @sock.write(buf)
-      @sock.write("\r\n")
+      rv = buf.bytesize
+      @sock.write("#{rv.to_s(16)}\r\n", buf, "\r\n")
       rv
     end
 

lib/net/protocol.rb

@@ -209,9 +209,9 @@ module Net # :nodoc:
 
     public
 
-    def write(str)
+    def write(*strs)
       writing {
-        write0 str
+        write0 *strs
       }
     end
 
@@ -235,9 +235,9 @@ module Net # :nodoc:
       bytes
     end
 
-    def write0(str)
-      @debug_output << str.dump if @debug_output
-      len = @io.write(str)
+    def write0(*strs)
+      @debug_output << strs.map(&:dump).join if @debug_output
+      len = @io.write(*strs)
       @written_bytes += len
       len
     end