cluster/tier: add watermarks and policy driver

Backport fix 12039

This fix introduces infrastructure to support different
policies for promotion and demotion.

Currently the tier feature automatically promotes and demotes
files periodically based on access. This is good for testing
but too stringent for most real workloads. It makes it
difficult to fully utilize a hot tier- data will be demoted
before it is touched- its unlikely a 100GB hot SSD will have
all its data touched in a window of time.

A new parameter "mode" allows the user to pick promotion/demotion
polcies.

The "test mode" will be used for *.t and other general testing.
This is the current mechanism.

The "cache mode" introduces watermarks. The watermarks
represent levels of data residing on the hot tier.

"cache mode" policy:

The % the hot tier is full is called P.

Do not promote or demote more than D MB or F files.

A random number [0-100] is called R.

Rules for migration:

if (P < watermark_low) don't demote, always promote.

if (P >= watermark_low) && (P < watermark_hi) demote if R < P; promote if R > P.

if (P > watermark_hi) always demote, don't promote.

gluster volume set {vol} cluster.watermark-hi %
gluster volume set {vol} cluster.watermark-low %
gluster volume set {vol} cluster.tier-max-mb {D}
gluster volume set {vol} cluster.tier-max-files {F}
gluster volume set {vol} cluster.tier-mode {test|cache}

> Change-Id: I157f19667ec95aa1d53406041c1e3b073be127c2
> BUG: 1257911
> Signed-off-by: Dan Lambright <dlambrig@redhat.com>
> Reviewed-on: http://review.gluster.org/12039
> Tested-by: Gluster Build System <jenkins@build.gluster.com>
> Reviewed-by: Atin Mukherjee <amukherj@redhat.com>
Signed-off-by: Dan Lambright <dlambrig@redhat.com>

Signed-off-by: Dan Lambright <dlambrig@redhat.com>

Conflicts:
	xlators/cluster/dht/src/dht-rebalance.c
	xlators/cluster/dht/src/tier.c

Change-Id: Ibfe6b89563ceab98708325cf5d5ab0997c64816c
BUG: 1270527
Reviewed-on: http://review.gluster.org/12330
Tested-by: NetBSD Build System <jenkins@build.gluster.org>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Dan Lambright <dlambrig@redhat.com>
Tested-by: Dan Lambright <dlambrig@redhat.com>

2 files changed, 23 insertions, 0 deletions

diff --git a/tests/basic/tier/tier.t b/tests/basic/tier/tier.t
index 80c31ea2430..55f66965183 100755
--- a/tests/basic/tier/tier.t
+++ b/tests/basic/tier/tier.t
@@ -150,12 +150,23 @@ TEST ! $CLI volume set $V0 cluster.tier-demote-frequency 4
 TEST ! $CLI volume tier $V0 detach commit force
 
 TEST $CLI volume tier $V0 attach replica 2 $H0:$B0/${V0}$CACHE_BRICK_FIRST $H0:$B0/${V0}$CACHE_BRICK_LAST
+
+TEST $CLI volume set $V0 cluster.tier-mode test
+
 # create a file, make sure it can be deleted after attach tier.
 TEST $GFS --volfile-id=/$V0 --volfile-server=$H0 $M0;
 cd $M0
 TEST touch delete_me.txt
 TEST rm -f delete_me.txt
 
+# confirm watermark CLI works
+TEST $CLI volume set $V0 cluster.watermark-hi 85
+TEST $CLI volume set $V0 cluster.watermark-low 75
+TEST $CLI volume set $V0 cluster.tier-max-mb 1000
+TEST $CLI volume set $V0 cluster.tier-max-files 1000
+TEST ! $CLI volume set $V0 cluster.tier-max-files -3
+TEST ! $CLI volume set $V0 cluster.watermark-low 90
+
 # stop the volume and restart it. The rebalance daemon should restart.
 TEST $CLI volume stop $V0
 TEST $CLI volume start $V0
diff --git a/tests/volume.rc b/tests/volume.rc
index 0000567a64d..e647dc3ae87 100644
--- a/tests/volume.rc
+++ b/tests/volume.rc
@@ -569,6 +569,18 @@ function get_snapd_count {
         ps auxww | grep glusterfs | grep snapd.pid | grep -v grep | wc -l
 }
 
+function drop_cache() {
+	case $OSTYPE in
+	Linux)
+		echo 3 > /proc/sys/vm/drop_caches
+		;;
+	*)
+		# fail but flush caches
+		( cd $1 && umount $1 2>/dev/null )
+		;;
+	esac
+}
+
 function quota_list_field () {
         local QUOTA_PATH=$1
         local FIELD=$2