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

[Steven Whitehouse <swhiteho@redhat.com>]

Hi,

That looks better. Do you get better results with it compared with the 
previous version?

Steve.

On 22/04/15 18:00, Bob Peterson wrote:
> 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 <rpeterso@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];
>