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GFS2: Use average srttb value in congestion calculations 

This patch changes function gfs2_rgrp_congested so that it uses an
average srttb (smoothed round trip time for blocking rgrp glocks)
rather than the CPU-specific value. If we use the CPU-specific value
it can incorrectly report no contention when there really is contention
due to the glock processing occurring on a different CPU.

Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Acked-by: Steven Whitehouse <swhiteho@redhat.com>
This commit is contained in:
Bob Peterson 2014-11-19 12:27:11 -06:00
parent bb0fd7ab09
commit f4a3ae9308
1 changed files with 9 additions and 4 deletions
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13
fs/gfs2/rgrp.c
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@ -1850,14 +1850,19 @@ static bool gfs2_rgrp_congested(const struct gfs2_rgrpd *rgd, int loops)
const struct gfs2_sbd *sdp = gl->gl_sbd;
struct gfs2_lkstats *st;
s64 r_dcount, l_dcount;
s64 r_srttb, l_srttb;
s64 l_srttb, a_srttb = 0;
s64 srttb_diff;
s64 sqr_diff;
s64 var;
int cpu;
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];
}
st = &this_cpu_ptr(sdp->sd_lkstats)->lkstats[LM_TYPE_RGRP];
r_srttb = st->stats[GFS2_LKS_SRTTB];
a_srttb /= num_present_cpus();
r_dcount = st->stats[GFS2_LKS_DCOUNT];
var = st->stats[GFS2_LKS_SRTTVARB] +
gl->gl_stats.stats[GFS2_LKS_SRTTVARB];
@ -1866,10 +1871,10 @@ static bool gfs2_rgrp_congested(const struct gfs2_rgrpd *rgd, int loops)
l_srttb = gl->gl_stats.stats[GFS2_LKS_SRTTB];
l_dcount = gl->gl_stats.stats[GFS2_LKS_DCOUNT];
if ((l_dcount < 1) || (r_dcount < 1) || (r_srttb == 0))
if ((l_dcount < 1) || (r_dcount < 1) || (a_srttb == 0))
return false;
srttb_diff = r_srttb - l_srttb;
srttb_diff = a_srttb - l_srttb;
sqr_diff = srttb_diff * srttb_diff;
var *= 2;