svn commit: r302288 - head/release/tools

Colin Percival cperciva at
Wed Jun 29 23:56:25 UTC 2016

Author: cperciva
Date: Wed Jun 29 23:56:24 2016
New Revision: 302288

  Enable indirect segment I/Os by default in the Xen blkfront driver when
  running on EC2.  Due to improvements in EC2, the performance penalty which
  was present on some EC2 instances no longer exists, and enabling this
  feature now consistently yields ~20% higher throughput with equal or lower
  Reverts:	r286063
  Approved by:	re (gjb)
  MFC after:	2 weeks
  Relnotes:	Improved disk throughput on EC2


Modified: head/release/tools/ec2.conf
--- head/release/tools/ec2.conf	Wed Jun 29 23:33:44 2016	(r302287)
+++ head/release/tools/ec2.conf	Wed Jun 29 23:56:24 2016	(r302288)
@@ -72,11 +72,6 @@ vm_extra_pre_umount() {
 	# nodes, but apply the workaround just in case.
 	echo 'hw.broken_txfifo="1"' >> ${DESTDIR}/boot/loader.conf
-	# Some EC2 instances suffer a significant (~40%) reduction in
-	# throughput when using blkif indirect segment I/Os.  Disable this
-	# by default for now.
-	echo 'hw.xbd.xbd_enable_indirect="0"' >> ${DESTDIR}/boot/loader.conf
 	# Some EC2 instances run on a version of Xen which has a bug relating
 	# to the migration of MSI-X interrupts; this is visible as SR-IOV
 	# networking (aka. "EC2 Enhanced Networking") not being able to pass

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