wbuf: bypass buffering if buffers are caught up

Sometimes buffering can catch up and we no longer need to
use the on-disk buffer, so keep trying to flush the data
out to the user to avoid VFS activity.

1 files changed, 12 insertions, 0 deletions

diff --git a/lib/yahns/wbuf.rb b/lib/yahns/wbuf.rb
index 4828056..df7d56d 100644
--- a/lib/yahns/wbuf.rb
+++ b/lib/yahns/wbuf.rb
@@ -14,6 +14,18 @@ class Yahns::Wbuf # :nodoc:
   end
 
   def wbuf_write(client, buf)
+    # try to bypass the VFS layer if we're all caught up
+    if @sf_count == 0
+      case rv = client.kgio_trywrite(buf)
+      when String
+        buf = rv # retry in loop
+      when nil
+        return nil # yay! hopefully we don't have to buffer again
+      when :wait_writable, :wait_readable
+        break # ugh, continue to buffering to file
+      end while true
+    end
+
     @sf_count += @tmpio.write(buf)
     case rv = client.trysendfile(@tmpio, @sf_offset, @sf_count)
     when Integer