Commit f4a3ae93 authored by Bob Peterson's avatar Bob Peterson
Browse files

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: default avatarBob Peterson <rpeterso@redhat.com>
Acked-by: default avatarSteven Whitehouse <swhiteho@redhat.com>
parent bb0fd7ab

fs/gfs2/rgrp.c

+9 −4
Original line number Diff line number Diff line
@@ -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;

CRA Git | Maintained and supported by SUSTech CRA and CCSE