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>

1 files changed, 9 insertions, 0 deletions

diff --git a/xlators/cluster/dht/src/dht-rebalance.c b/xlators/cluster/dht/src/dht-rebalance.c
index 6471d54cdfe..69c64816909 100644
--- a/xlators/cluster/dht/src/dht-rebalance.c
+++ b/xlators/cluster/dht/src/dht-rebalance.c
@@ -1331,6 +1331,15 @@ dht_migrate_file (xlator_t *this, loc_t *loc, xlator_t *from, xlator_t *to,
                 }
         }
 
+        /* store size of previous migrated file  */
+        if (defrag->tier_conf.is_tier) {
+                if (from == conf->subvolumes[0]) {
+                        defrag->tier_conf.st_last_promoted_size = stbuf.ia_size;
+                } else {
+                        defrag->tier_conf.st_last_demoted_size = stbuf.ia_size;
+                }
+        }
+
         /* The src file is being unlinked after this so we don't need
            to clean it up */
         clean_src = _gf_false;