core: Do internal latency measurement of FOPs.

This patch adds a facility by which each translator
keeps track of the average latency of a FOP from
its point of view. That is, the duration between
the translator handing over the call to a lower-level
translator and the reply coming back.

The latency measurement is off by default, and can
be toggled by sending SIGUSR2 to the GlusterFS process.

Latency data is printed as part of the process state dump.

Signed-off-by: Vikas Gorur <vikas@gluster.com>
Signed-off-by: Anand V. Avati <avati@dev.gluster.com>

BUG: 268 (Add timing instrumentation code)
URL: http://bugs.gluster.com/cgi-bin/bugzilla3/show_bug.cgi?id=268

1 files changed, 36 insertions, 0 deletions

diff --git a/libglusterfs/src/latency.h b/libglusterfs/src/latency.h
new file mode 100644
index 00000000..ba7d76cd
--- /dev/null
+++ b/libglusterfs/src/latency.h
@@ -0,0 +1,36 @@
+/*
+  Copyright (c) 2009 Gluster, Inc. <http://www.gluster.com>
+  This file is part of GlusterFS.
+
+  GlusterFS is free software; you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published
+  by the Free Software Foundation; either version 3 of the License,
+  or (at your option) any later version.
+
+  GlusterFS is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+  General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program.  If not, see
+  <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __LATENCY_H__
+#define __LATENCY_H__
+
+
+typedef struct fop_latency {
+        uint64_t min;           /* min time for the call (microseconds) */
+        uint64_t max;           /* max time for the call (microseconds) */
+	double total;           /* total time (microseconds) */
+        double std;             /* standard deviation */
+        double mean;            /* mean (microseconds) */
+        uint64_t count;
+} fop_latency_t;
+
+void
+gf_latency_toggle (int signum);
+
+#endif /* __LATENCY_H__ */