+/**
+ * gfs2_update_stats - Update time based stats
+ * @mv: Pointer to mean/variance structure to update
+ * @sample: New data to include
+ *
+ * @delta is the difference between the current rtt sample and the
+ * running average srtt. We add 1/8 of that to the srtt in order to
+ * update the current srtt estimate. The varience estimate is a bit
+ * more complicated. We subtract the abs value of the @delta from
+ * the current variance estimate and add 1/4 of that to the running
+ * total.
+ *
+ * Note that the index points at the array entry containing the smoothed
+ * mean value, and the variance is always in the following entry
+ *
+ * Reference: TCP/IP Illustrated, vol 2, p. 831,832
+ * All times are in units of integer nanoseconds. Unlike the TCP/IP case,
+ * they are not scaled fixed point.
+ */
+
+static inline void gfs2_update_stats(struct gfs2_lkstats *s, unsigned index,
+ s64 sample)
+{
+ s64 delta = sample - s->stats[index];
+ s->stats[index] += (delta >> 3);
+ index++;
+ s->stats[index] += ((abs64(delta) - s->stats[index]) >> 2);
+}
+
+/**
+ * gfs2_update_reply_times - Update locking statistics
+ * @gl: The glock to update
+ *
+ * This assumes that gl->gl_dstamp has been set earlier.
+ *
+ * The rtt (lock round trip time) is an estimate of the time
+ * taken to perform a dlm lock request. We update it on each
+ * reply from the dlm.
+ *
+ * The blocking flag is set on the glock for all dlm requests
+ * which may potentially block due to lock requests from other nodes.
+ * DLM requests where the current lock state is exclusive, the
+ * requested state is null (or unlocked) or where the TRY or
+ * TRY_1CB flags are set are classified as non-blocking. All
+ * other DLM requests are counted as (potentially) blocking.
+ */
+static inline void gfs2_update_reply_times(struct gfs2_glock *gl)
+{
+ struct gfs2_pcpu_lkstats *lks;
+ const unsigned gltype = gl->gl_name.ln_type;
+ unsigned index = test_bit(GLF_BLOCKING, &gl->gl_flags) ?
+ GFS2_LKS_SRTTB : GFS2_LKS_SRTT;
+ s64 rtt;
+
+ preempt_disable();
+ rtt = ktime_to_ns(ktime_sub(ktime_get_real(), gl->gl_dstamp));
+ lks = this_cpu_ptr(gl->gl_sbd->sd_lkstats);
+ gfs2_update_stats(&gl->gl_stats, index, rtt); /* Local */
+ gfs2_update_stats(&lks->lkstats[gltype], index, rtt); /* Global */
+ preempt_enable();
+
+ trace_gfs2_glock_lock_time(gl, rtt);
+}
+
+/**
+ * gfs2_update_request_times - Update locking statistics
+ * @gl: The glock to update
+ *
+ * The irt (lock inter-request times) measures the average time
+ * between requests to the dlm. It is updated immediately before
+ * each dlm call.
+ */
+
+static inline void gfs2_update_request_times(struct gfs2_glock *gl)
+{
+ struct gfs2_pcpu_lkstats *lks;
+ const unsigned gltype = gl->gl_name.ln_type;
+ ktime_t dstamp;
+ s64 irt;
+
+ preempt_disable();
+ dstamp = gl->gl_dstamp;
+ gl->gl_dstamp = ktime_get_real();
+ irt = ktime_to_ns(ktime_sub(gl->gl_dstamp, dstamp));
+ lks = this_cpu_ptr(gl->gl_sbd->sd_lkstats);
+ gfs2_update_stats(&gl->gl_stats, GFS2_LKS_SIRT, irt); /* Local */
+ gfs2_update_stats(&lks->lkstats[gltype], GFS2_LKS_SIRT, irt); /* Global */
+ preempt_enable();
+}
+