[PATCH] reduce syscalls in recvmsg invocations

[PATCH] reduce syscalls in recvmsg invocations

[Eric Wong]

Favor IO.select over IO#wait since the latter makes another
ioctl syscall (which we'll make anyways for IO#nread).

Having BasicSocket#recvmsg and recvmsg_nonblock detect the buffer
size requires extra syscalls, so pass explict maxmesglen, flags, and
maxcontrollen args to elide auto-detection since we already have the
buffered amount from IO#nread.

This cuts more syscalls from the "dtas-tl cat" invocation with
larger tracklists.
---
 lib/dtas/unix_accepted.rb | 2 +-
 lib/dtas/unix_client.rb   | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/lib/dtas/unix_accepted.rb b/lib/dtas/unix_accepted.rb
index 2c82d2a..3008afc 100644
--- a/lib/dtas/unix_accepted.rb
+++ b/lib/dtas/unix_accepted.rb
@@ -56,7 +56,7 @@ class DTAS::UNIXAccepted # :nodoc:
 
     begin
       begin
-        msg, _, _ = io.recvmsg_nonblock(nread)
+        msg, _, _ = io.recvmsg_nonblock(nread, 0, 0)
       rescue Errno::EAGAIN
         return :wait_readable
       rescue EOFError, SystemCallError
diff --git a/lib/dtas/unix_client.rb b/lib/dtas/unix_client.rb
index 40dedcc..7382ea6 100644
--- a/lib/dtas/unix_client.rb
+++ b/lib/dtas/unix_client.rb
@@ -38,9 +38,9 @@ class DTAS::UNIXClient # :nodoc:
   end
 
   def res_wait(timeout = nil)
-    @to_io.wait(timeout)
+    IO.select([@to_io], nil, nil, timeout)
     nr = @to_io.nread
     nr > 0 or raise EOFError, "unexpected EOF from server"
-    @to_io.recvmsg[0]
+    @to_io.recvmsg(nr, 0, 0)[0]
   end
 end
-- 
EW