mount/fuse: Make event-history feature configurable

... and disable it by default.

        Backport of:
        > Change-Id: Ia533788d309c78688a315dc8cd04d30fad9e9485
        > Reviewed-on: https://review.gluster.org/18242
        > BUG: 1467614
        > cherry-picked from commit 956d43d6e89d40ee683547003b876f1f456f03b6

This is because having it disabled seems to improve performance.
This could be due to the lock contention by the different epoll threads
on the circular buff lock in the fop cbks just before writing their response
to /dev/fuse.

Just to provide some data - wrt ovirt-gluster hyperconverged
environment, I saw an increase in IOPs by 12K with event-history
disabled for randrom read workload.

Usage:
mount -t glusterfs -o event-history=on $HOSTNAME:$VOLNAME $MOUNTPOINT
OR
glusterfs --event-history=on --volfile-server=$HOSTNAME --volfile-id=$VOLNAME $MOUNTPOINT

Change-Id: Ia533788d309c78688a315dc8cd04d30fad9e9485
BUG: 1495397
Signed-off-by: Krutika Dhananjay <kdhananj@redhat.com>

1 files changed, 25 insertions, 9 deletions

diff --git a/xlators/mount/fuse/src/fuse-bridge.c b/xlators/mount/fuse/src/fuse-bridge.c
index 4865ffdc562..d7c213425c6 100644
--- a/xlators/mount/fuse/src/fuse-bridge.c
+++ b/xlators/mount/fuse/src/fuse-bridge.c
@@ -5162,10 +5162,15 @@ fuse_priv_dump (xlator_t  *this)
 int
 fuse_history_dump (xlator_t *this)
 {
-        int      ret    = -1;
-        char key_prefix[GF_DUMP_MAX_BUF_LEN] = {0,};
+        int             ret                             = -1;
+        char            key_prefix[GF_DUMP_MAX_BUF_LEN] = {0,};
+        fuse_private_t *priv                            = this->private;
 
         GF_VALIDATE_OR_GOTO ("fuse", this, out);
+
+        if (!priv->event_history)
+                goto out;
+
         GF_VALIDATE_OR_GOTO (this->name, this->history, out);
 
         gf_proc_dump_build_key (key_prefix, "xlator.mount.fuse",
@@ -5660,6 +5665,9 @@ init (xlator_t *this_xl)
                 }
         }
 
+        GF_OPTION_INIT("event-history", priv->event_history, bool,
+                       cleanup_exit);
+
         /* user has set only background-qlen, not congestion-threshold,
            use the fuse kernel driver formula to set congestion. ie, 75% */
         if (dict_get (this_xl->options, "background-qlen") &&
@@ -5758,14 +5766,16 @@ init (xlator_t *this_xl)
                         goto cleanup_exit;
         }
 
-        event = eh_new (FUSE_EVENT_HISTORY_SIZE, _gf_false, NULL);
-        if (!event) {
-                gf_log (this_xl->name, GF_LOG_ERROR,
-                        "could not create a new event history");
-                goto cleanup_exit;
-        }
+        if (priv->event_history) {
+                event = eh_new (FUSE_EVENT_HISTORY_SIZE, _gf_false, NULL);
+                if (!event) {
+                        gf_log (this_xl->name, GF_LOG_ERROR,
+                                "could not create a new event history");
+                        goto cleanup_exit;
+                }
 
-        this_xl->history = event;
+                this_xl->history = event;
+        }
 
         pthread_mutex_init (&priv->fuse_dump_mutex, NULL);
         pthread_cond_init (&priv->sync_cond, NULL);
@@ -5962,5 +5972,11 @@ struct volume_options options[] = {
           .type = GF_OPTION_TYPE_BOOL,
           .default_value = "false"
         },
+        { .key = {"event-history"},
+          .type = GF_OPTION_TYPE_BOOL,
+          .default_value = "false",
+          .description = "This option can be used to enable or disable fuse "
+          "event history.",
+        },
         { .key = {NULL} },
 };