[Cluster-devel] [GFS2 PATCH] GFS2: Average in only non-zero round-trip times for congestion stats

[Bob Peterson]

Hi,

This patch changes function gfs2_rgrp_congested so that it only factors
in non-zero values into its average round trip time. If the round-trip
time is zero for a particular cpu, that cpu has obviously never dealt
with bouncing the resource group in question, so factoring in a zero
value will only skew the numbers. It also fixes a compile error on
some arches related to division.

Regards,

Bob Peterson
Signed-off-by: Bob Peterson <rpete...@redhat.com>
---
diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c
index f39eedc..cb27065 100644
--- a/fs/gfs2/rgrp.c
+++ b/fs/gfs2/rgrp.c
@@ -1854,15 +1854,19 @@ static bool gfs2_rgrp_congested(const struct gfs2_rgrpd 
*rgd, int loops)
        s64 srttb_diff;
        s64 sqr_diff;
        s64 var;
-       int cpu;
+       int cpu, nonzero = 0;
 
        preempt_disable();
        for_each_present_cpu(cpu) {
                st = &per_cpu_ptr(sdp->sd_lkstats, cpu)->lkstats[LM_TYPE_RGRP];
-               a_srttb += st->stats[GFS2_LKS_SRTTB];
+               if (st->stats[GFS2_LKS_SRTTB]) {
+                       a_srttb += st->stats[GFS2_LKS_SRTTB];
+                       nonzero++;
+               }
        }
        st = &this_cpu_ptr(sdp->sd_lkstats)->lkstats[LM_TYPE_RGRP];
-       a_srttb /= num_present_cpus();
+       if (nonzero)
+               do_div(a_srttb, nonzero);
        r_dcount = st->stats[GFS2_LKS_DCOUNT];
        var = st->stats[GFS2_LKS_SRTTVARB] +
              gl->gl_stats.stats[GFS2_LKS_SRTTVARB];