Hi,
On 15/04/15 15:39, Bob Peterson wrote:
Hi,
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 <[email protected]>
Looks like a good catch... Acked-by: Steven Whitehouse <[email protected]>
Steve.
---
diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c
index 6af2396..f39eedc 100644
--- a/fs/gfs2/rgrp.c
+++ b/fs/gfs2/rgrp.c
@@ -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;
