From: "Dumitrescu, Cristian" <cristian.dumitrescu@intel.com>
To: Nikhil Jagtap <nikhil.jagtap@gmail.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>,
"Ramia, Kannan Babu" <kannan.babu.ramia@intel.com>
Subject: Re: [dpdk-dev] [PATCH] meter: fix excess token bucket update in srtcm implementation
Date: Mon, 19 Sep 2016 15:51:47 +0000 [thread overview]
Message-ID: <3EB4FA525960D640B5BDFFD6A3D8912647A83BBA@IRSMSX108.ger.corp.intel.com> (raw)
In-Reply-To: <1473228910-10429-1-git-send-email-nikhil.jagtap@gmail.com>
> -----Original Message-----
> From: Nikhil Jagtap [mailto:nikhil.jagtap@gmail.com]
> Sent: Wednesday, September 7, 2016 7:15 AM
> To: Dumitrescu, Cristian <cristian.dumitrescu@intel.com>
> Cc: dev@dpdk.org; Ramia, Kannan Babu <kannan.babu.ramia@intel.com>;
> Nikhil Jagtap <nikhil.jagtap@gmail.com>
> Subject: [PATCH] meter: fix excess token bucket update in srtcm
> implementation
>
> As per srTCM RFC 2697, we should be updating the E bucket only after the
> C bucket overflows. This patch fixes the current DPDK implementation,
> where we are updating both the buckets simultaneously at the same rate
> (CIR) which results in token accumulation rate of (2*CIR).
>
> Signed-off-by: Nikhil Jagtap <nikhil.jagtap@gmail.com>
> ---
> lib/librte_meter/rte_meter.h | 26 ++++++++++++++++----------
> 1 files changed, 16 insertions(+), 10 deletions(-)
>
> diff --git a/lib/librte_meter/rte_meter.h b/lib/librte_meter/rte_meter.h
> index 2cd8d81..0ffcb60 100644
> --- a/lib/librte_meter/rte_meter.h
> +++ b/lib/librte_meter/rte_meter.h
> @@ -232,13 +232,16 @@ rte_meter_srtcm_color_blind_check(struct
> rte_meter_srtcm *m,
> n_periods = time_diff / m->cir_period;
> m->time += n_periods * m->cir_period;
>
> + /* Put the tokens overflowing from tc into te bucket */
> tc = m->tc + n_periods * m->cir_bytes_per_period;
> - if (tc > m->cbs)
> + if (tc > m->cbs) {
> + te = m->te + (tc - m->cbs);
> + if (te > m->ebs)
> + te = m->ebs;
> tc = m->cbs;
> -
> - te = m->te + n_periods * m->cir_bytes_per_period;
> - if (te > m->ebs)
> - te = m->ebs;
> + } else {
> + te = m->te;
> + }
Just to avoid the final else, in order to have the critical path (Tc not overflowing) as the default fall-through code path, I suggest the following small change in the code (update the Te just after Tc update, for the case of Tc overflowing), which should favour the usage of the cmov instruction:
/* Put the tokens overflowing from tc into te bucket */
tc = m->tc + n_periods * m->cir_bytes_per_period;
te = m->te;
if (tc > m->cbs) {
te = m->te + (tc - m->cbs);
if (te > m->ebs)
te = m->ebs;
tc = m->cbs;
}
Are you OK with this change?
>
> /* Color logic */
> if (tc >= pkt_len) {
> @@ -271,13 +274,16 @@ rte_meter_srtcm_color_aware_check(struct
> rte_meter_srtcm *m,
> n_periods = time_diff / m->cir_period;
> m->time += n_periods * m->cir_period;
>
> + /* Put the tokens overflowing from tc into te bucket */
> tc = m->tc + n_periods * m->cir_bytes_per_period;
> - if (tc > m->cbs)
> + if (tc > m->cbs) {
> + te = m->te + (tc - m->cbs);
> + if (te > m->ebs)
> + te = m->ebs;
> tc = m->cbs;
> -
> - te = m->te + n_periods * m->cir_bytes_per_period;
> - if (te > m->ebs)
> - te = m->ebs;
> + } else {
> + te = m->te;
> + }
Same as above.
>
> /* Color logic */
> if ((pkt_color == e_RTE_METER_GREEN) && (tc >= pkt_len)) {
> --
> 1.7.1
next prev parent reply other threads:[~2016-09-19 15:51 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-07 6:15 Nikhil Jagtap
2016-09-19 15:51 ` Dumitrescu, Cristian [this message]
2016-09-20 4:40 ` Nikhil Jagtap
2016-09-21 5:57 ` [dpdk-dev] [PATCH v2] " Nikhil Jagtap
2016-09-21 8:57 ` Dumitrescu, Cristian
2016-09-21 21:19 ` Thomas Monjalon
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