core: Global timer-wheel

Instantiate a process wide global instance of the timer wheel
data structure. Spawning glusterfs* process with option arg
"--global-timer-wheel" instantiates a global instance of
timer-wheel under global context (->ctx).

Translators can make use of this process wide instance [via a
call to glusterfs_global_timer_wheel()] instead of maintaining
an instance of their own and possibly consuming more memory.
Linux kernel too has a single instance of timer wheel where
subsystems such as IO, networking, etc.. make use of.

Bitrot daemon would be early consumers of this: bitrot translator
instances for multiple volumes would track objects belonging to
their respective bricks in this global expiry tracking data
structure. This is also a first step to move GlusterFS timer
mechanism to use timer-wheel.

> Change-Id: Ie882df607e07acaced846ea269ebf1ece306d6ae
> BUG: 1170075
> Signed-off-by: Venky Shankar <vshankar@redhat.com>
> Reviewed-on: http://review.gluster.org/10380
> Tested-by: NetBSD Build System
> Reviewed-by: Vijay Bellur <vbellur@redhat.com>
> Tested-by: Gluster Build System <jenkins@build.gluster.com>

Change-Id: I35c840daa9996a059699f8ea5af54c76ede7e09c
Signed-off-by: Venky Shankar <vshankar@redhat.com>
Signed-off-by: Gaurav Kumar Garg <ggarg@redhat.com>
BUG: 1220041
Reviewed-on: http://review.gluster.org/10716
Tested-by: Gluster Build System <jenkins@build.gluster.com>

1 files changed, 25 insertions, 0 deletions

diff --git a/libglusterfs/src/tw.c b/libglusterfs/src/tw.c
new file mode 100644
index 00000000000..fa11998aace
--- /dev/null
+++ b/libglusterfs/src/tw.c
@@ -0,0 +1,25 @@
+/*
+  Copyright (c) 2008-2015 Red Hat, Inc. <http://www.redhat.com>
+  This file is part of GlusterFS.
+
+  This file is licensed to you under your choice of the GNU Lesser
+  General Public License, version 3 or any later version (LGPLv3 or
+  later), or the GNU General Public License, version 2 (GPLv2), in all
+  cases as published by the Free Software Foundation.
+*/
+
+#include "tw.h"
+#include "timer-wheel.h"
+
+int
+glusterfs_global_timer_wheel_init (glusterfs_ctx_t *ctx)
+{
+        ctx->timer_wheel = gf_tw_init_timers();
+        return ctx->timer_wheel ? 0 : -1;
+}
+
+struct tvec_base *
+glusterfs_global_timer_wheel (xlator_t *this)
+{
+        return this->ctx->timer_wheel;
+}