Rev 5346: (mbp) document some tricks about testing bzr (tmpfs, tc qdisc, in file:///home/pqm/archives/thelove/bzr/%2Btrunk/

[Canonical.com Patch Queue Manager]

At file:///home/pqm/archives/thelove/bzr/%2Btrunk/

------------------------------------------------------------
revno: 5346 [merge]
revision-id: pqm at pqm.ubuntu.com-20100715110657-zb7pmrur0azigjs5
parent: pqm at pqm.ubuntu.com-20100713224310-irt5swwo7ajwg7e5
parent: mbp at canonical.com-20100715094716-sljdg6go0d12xi79
committer: Canonical.com Patch Queue Manager <pqm at pqm.ubuntu.com>
branch nick: +trunk
timestamp: Thu 2010-07-15 12:06:57 +0100
message:
  (mbp) document some tricks about testing bzr (tmpfs, tc qdisc,
   parallel) (Martin Pool)
modified:
  doc/developers/testing.txt     testing.txt-20080812140359-i70zzh6v2z7grqex-1
=== modified file 'doc/developers/testing.txt'
--- a/doc/developers/testing.txt	2010-06-24 07:11:55 +0000
+++ b/doc/developers/testing.txt	2010-07-15 09:47:16 +0000
@@ -193,6 +193,41 @@
 <http://babune.ladeuil.net:24842/>.  (Babune = Bazaar Buildbot Network.)
 
 
+Running tests in parallel
+-------------------------
+
+Bazaar can use subunit to spawn multiple test processes.  There is
+slightly more chance you will hit ordering or timing-dependent bugs but
+it's much faster::
+
+  $ ./bzr selftest --parallel=fork
+
+Note that you will need the Subunit library
+<https://launchpad.net/subunit/> to use this, which is in
+``python-subunit`` on Ubuntu.
+
+
+Running tests from a ramdisk
+----------------------------
+
+The tests create and delete a lot of temporary files.  In some cases you
+can make the test suite run much faster by running it on a ramdisk.  For
+example::
+
+  $ sudo mkdir /ram
+  $ sudo mount -t tmpfs none /ram
+  $ TMPDIR=/ram ./bzr selftest ...
+
+You could also change ``/tmp`` in ``/etc/fstab`` to have type ``tmpfs``,
+if you don't mind possibly losing other files in there when the machine
+restarts.  Add this line (if there is none for ``/tmp`` already)::
+
+  none           /tmp            tmpfs  defaults        0       0
+
+With a 6-core machine and ``--parallel=fork`` using a tmpfs doubles the
+test execution speed.
+
+
 Writing Tests
 =============
 
@@ -889,6 +924,44 @@
 (The same facility is available outside of tests through
 ``bzrlib.cleanup``.)
 
+
+Manual testing
+==============
+
+Generally we prefer automated testing but sometimes a manual test is the
+right thing, especially for performance tests that want to measure elapsed
+time rather than effort.
+
+Simulating slow networks
+------------------------
+
+To get realistically slow network performance for manually measuring
+performance, we can simulate 500ms latency (thus 1000ms round trips)::
+
+  $ sudo tc qdisc add dev lo root netem delay 500ms
+
+Normal system behaviour is restored with ::
+
+  $ sudo tc qdisc del dev lo root
+
+A more precise version that only filters traffic to port 4155 is::
+
+    tc qdisc add dev lo root handle 1: prio
+    tc qdisc add dev lo parent 1:3 handle 30: netem delay 500ms 
+    tc qdisc add dev lo parent 30:1 handle 40: prio
+    tc filter add dev lo protocol ip parent 1:0 prio 3 u32 match ip dport 4155 0xffff flowid 1:3 handle 800::800
+    tc filter add dev lo protocol ip parent 1:0 prio 3 u32 match ip sport 4155 0xffff flowid 1:3 handle 800::801
+
+and to remove this::
+
+    tc filter del dev lo protocol ip parent 1: pref 3 u32
+    tc qdisc del dev lo root handle 1:
+
+You can use similar code to add additional delay to a real network
+interface, perhaps only when talking to a particular server or pointing at
+a VM.  For more information see <http://lartc.org/>.
+
+
 .. |--| unicode:: U+2014
 
 ..