performance/readdir-ahead: introduce directory read-ahead translator

This is a translator to improve the performance of typical,
sequential directory reads (i.e., ls). readdir-ahead begins
preloading the contents of a directory on open and serves readdir
requests from the preloaded content. readdir-ahead is currently
implemented to only handle the single threaded directory read
case.

readdir-ahead is currently disabled by default. It can be enabled
with the following command:

	gluster volume set <volname> readdir-ahead on

The following are results of a getdents test on a single brick
volume.

Test info:

- Single VM, gluster client/server.
- Volume mounted with native client using --gid-timeout=2.
- getdents on single directory with 100k 0-byte files.

Test results:

- !readdir-ahead

read 3120080 bytes from offset 0
3 MiB, 4348 ops, 0:00:07.00 (416.590 KiB/sec and 594.4737 ops/sec)

- readdir-ahead

read 3120080 bytes from offset 0
3 MiB, 4348 ops, 0:00:03.00 (820.116 KiB/sec and 1170.3043 ops/sec)

BUG: 980517
Change-Id: Ieceb9e1eb47d1d5b5af8da2bf03839537364653f
Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-on: http://review.gluster.org/4519
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>

1 files changed, 44 insertions, 0 deletions

diff --git a/tests/features/readdir-ahead.t b/tests/features/readdir-ahead.t
new file mode 100755
index 00000000000..c7ee637f0b2
--- /dev/null
+++ b/tests/features/readdir-ahead.t
@@ -0,0 +1,44 @@
+#!/bin/bash
+#
+# Test basic readdir-ahead functionality. Verify that readdir-ahead can be
+# enabled, create a set of files and run some ls tests.
+#
+###
+
+. $(dirname $0)/../include.rc
+
+cleanup;
+
+TEST glusterd
+
+TEST $CLI volume create $V0 $H0:$B0/$V0
+TEST $CLI volume start $V0
+
+TEST $CLI volume set $V0 readdir-ahead on
+
+TEST glusterfs --volfile-id=$V0 --volfile-server=$H0 $M0
+
+TEST mkdir $M0/test
+for i in $(seq 0 99)
+do
+	touch $M0/test/$i
+done
+
+count=`ls -1 $M0/test | wc -l`
+TEST [ $count -eq 100 ]
+
+count=`ls -1 $M0/test | wc -l`
+TEST [ $count -eq 100 ]
+
+TEST rm -rf $M0/test/*
+
+count=`ls -1 $M0/test | wc -l`
+TEST [ $count -eq 0 ]
+
+TEST rmdir $M0/test
+
+TEST umount -l $M0;
+TEST $CLI volume stop $V0
+TEST $CLI volume delete $V0
+
+cleanup;