Hi Bhanu
Thanks for your efforts.
The reason I sent this e-mail regarding patch 5 is that as is, it could not be
merged.
Since, I have not seen the incremental changes (used in some referred customer
testing) beyond this, I wanted to
give a reasonable chance to evaluate the full changes.
Cheers Darrell
-----Original Message-----
From: "Bodireddy, Bhanuprakash" <bhanuprakash.bodire...@intel.com>
Date: Friday, August 11, 2017 at 6:11 AM
To: Darrell Ball <db...@vmware.com>, "d...@openvswitch.org"
<d...@openvswitch.org>, Ilya Maximets <i.maxim...@samsung.com>, Jan Scheurich
<jan.scheur...@ericsson.com>, Eelco Chaudron <echau...@redhat.com>
Cc: Ben Pfaff <b...@ovn.org>, "Stokes, Ian" <ian.sto...@intel.com>, "Gray, Mark
D" <mark.d.g...@intel.com>, "Fischetti, Antonio" <antonio.fische...@intel.com>,
Kevin Traynor <ktray...@redhat.com>
Subject: RE: [ovs-dev] [PATCH v4 5/5] dpif-netdev: Flush the packets in
intermediate queue.
Hello All,
Adding all the people here who had either reviewed or provided their
feedback
on the batching patches at some stage.
you are already aware that there are 2 different series on ML to implement
tx
batching (netdev layer vs dpif layer) that improves DPDK datapath
performance.
Our output batching is in netdev layer whereas ilya moved it to dpif layer
and simplified it. Each approach has its own pros and cons and had been
discussed in earlier threads.
While reviewing v4 of my patch series, ilya detected a race condition that
happens
when the queues in the guest are enabled/disabled at run time. Though we
have
solutions to address this issue and implemented it, I realized that the
code complexity
has increased and changes spanning multiple functions with additional spin
locks to
address this one corner case.
I think, though our patch series has flexibility it has gotten lot complex
now and would
be difficult to maintain in the future. At this stage I would like to lean
towards simpler
solution that's more maintainable which is implemented by Ilya.
I would like to thank Eelco, Darrell, Jan and Ilya for reviewing our series
and providing their
feedback.
Bhanuprakash.
>-----Original Message-----
>From: Darrell Ball [mailto:db...@vmware.com]
>Sent: Friday, August 11, 2017 2:03 AM
>To: Bodireddy, Bhanuprakash <bhanuprakash.bodire...@intel.com>;
>d...@openvswitch.org
>Subject: Re: [ovs-dev] [PATCH v4 5/5] dpif-netdev: Flush the packets in
>intermediate queue.
>
>Hi Bhanu
>
>Given that you ultimately intend changes beyond those in this patch, would
it
>make sense just to fold the follow up series (at least, the key elements)
into
>this series, essentially expanding on this patch 5 ?
>
>Thanks Darrell
>
>-----Original Message-----
>From: <ovs-dev-boun...@openvswitch.org> on behalf of Bhanuprakash
>Bodireddy <bhanuprakash.bodire...@intel.com>
>Date: Tuesday, August 8, 2017 at 10:06 AM
>To: "d...@openvswitch.org" <d...@openvswitch.org>
>Subject: [ovs-dev] [PATCH v4 5/5] dpif-netdev: Flush the packets in
> intermediate queue.
>
> Under low rate traffic conditions, there can be 2 issues.
> (1) Packets potentially can get stuck in the intermediate queue.
> (2) Latency of the packets can increase significantly due to
> buffering in intermediate queue.
>
> This commit handles the (1) issue by flushing the tx port queues using
> dp_netdev_flush_txq_ports() as part of PMD packet processing loop.
> Also this commit addresses issue (2) by flushing the tx queues after
> every rxq port processing. This reduces the latency with out impacting
> the forwarding throughput.
>
> MASTER
> --------
> Pkt size min(ns) avg(ns) max(ns)
> 512 4,631 5,022 309,914
> 1024 5,545 5,749 104,294
> 1280 5,978 6,159 45,306
> 1518 6,419 6,774 946,850
>
> MASTER + COMMIT
> -----------------
> Pkt size min(ns) avg(ns) max(ns)
> 512 4,711 5,064 182,477
> 1024 5,601 5,888 701,654
> 1280 6,018 6,491 533,037
> 1518 6,467 6,734 312,471
>
> PMDs can be teared down and spawned at runtime and so the rxq and txq
> mapping of the PMD threads can change. In few cases packets can get
> stuck in the queue due to reconfiguration and this commit helps flush
> the queues.
>
> Suggested-by: Eelco Chaudron <echau...@redhat.com>
> Reported-at: https://urldefense.proofpoint.com/v2/url?u=https-
>3A__mail.openvswitch.org_pipermail_ovs-2Ddev_2017-
>2DApril_331039.html&d=DwICAg&c=uilaK90D4TOVoH58JNXRgQ&r=BVhFA09C
>GX7JQ5Ih-
>uZnsw&m=qwwXxtIBvUf5cgPbYkcAKwCukS_ZiaeFE6lAdHHaw28&s=H0yNRh-
>c9pdYHacCzkoruc48Dj_Whkcwcjzv-vta-EI&e=
> Signed-off-by: Bhanuprakash Bodireddy
><bhanuprakash.bodire...@intel.com>
> Signed-off-by: Antonio Fischetti <antonio.fische...@intel.com>
> Co-authored-by: Antonio Fischetti <antonio.fische...@intel.com>
> Signed-off-by: Markus Magnusson <markus.magnus...@ericsson.com>
> Co-authored-by: Markus Magnusson <markus.magnus...@ericsson.com>
> Acked-by: Eelco Chaudron <echau...@redhat.com>
> ---
> lib/dpif-netdev.c | 52
>+++++++++++++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 51 insertions(+), 1 deletion(-)
>
> diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
> index e2cd931..bfb9650 100644
> --- a/lib/dpif-netdev.c
> +++ b/lib/dpif-netdev.c
> @@ -340,6 +340,7 @@ enum pmd_cycles_counter_type {
> };
>
> #define XPS_TIMEOUT_MS 500LL
> +#define LAST_USED_QID_NONE -1
>
> /* Contained by struct dp_netdev_port's 'rxqs' member. */
> struct dp_netdev_rxq {
> @@ -500,7 +501,13 @@ struct rxq_poll {
> struct tx_port {
> struct dp_netdev_port *port;
> int qid;
> - long long last_used;
> + int last_used_qid; /* Last queue id where packets got
> + enqueued. */
> + long long last_used; /* In case XPS is enabled, it contains
the
> + * timestamp of the last time the port
was
> + * used by the thread to send data.
After
> + * XPS_TIMEOUT_MS elapses the qid will
be
> + * marked as -1. */
> struct hmap_node node;
> };
>
> @@ -3101,6 +3108,25 @@ cycles_count_intermediate(struct
>dp_netdev_pmd_thread *pmd,
> non_atomic_ullong_add(&pmd->cycles.n[type], interval);
> }
>
> +static void
> +dp_netdev_flush_txq_ports(struct dp_netdev_pmd_thread *pmd)
> +{
> + struct tx_port *cached_tx_port;
> + int tx_qid;
> +
> + HMAP_FOR_EACH (cached_tx_port, node, &pmd->send_port_cache) {
> + tx_qid = cached_tx_port->last_used_qid;
> +
> + if (tx_qid != LAST_USED_QID_NONE) {
> + netdev_txq_flush(cached_tx_port->port->netdev, tx_qid,
> + cached_tx_port->port->dynamic_txqs);
> +
> + /* Queue flushed and mark it empty. */
> + cached_tx_port->last_used_qid = LAST_USED_QID_NONE;
> + }
> + }
> +}
> +
> static int
> dp_netdev_process_rxq_port(struct dp_netdev_pmd_thread *pmd,
> struct netdev_rxq *rx,
> @@ -3667,6 +3693,9 @@ dpif_netdev_run(struct dpif *dpif)
> dp_netdev_process_rxq_port(non_pmd,
> port->rxqs[i].rx,
> port->port_no);
> +
> + dp_netdev_flush_txq_ports(non_pmd);
> +
> cycles_count_intermediate(non_pmd,
process_packets ?
>
PMD_CYCLES_PROCESSING
> :
PMD_CYCLES_IDLE);
> @@ -3854,6 +3883,8 @@ reload:
> process_packets =
> dp_netdev_process_rxq_port(pmd, poll_list[i].rx,
> poll_list[i].port_no);
> + dp_netdev_flush_txq_ports(pmd);
> +
> cycles_count_intermediate(pmd,
> process_packets ?
PMD_CYCLES_PROCESSING
> :
PMD_CYCLES_IDLE);
> @@ -3879,6 +3910,9 @@ reload:
>
> cycles_count_end(pmd, PMD_CYCLES_IDLE);
>
> + /* Flush the queues as part of reconfiguration logic. */
> + dp_netdev_flush_txq_ports(pmd);
> +
> poll_cnt = pmd_load_queues_and_ports(pmd, &poll_list);
> exiting = latch_is_set(&pmd->exit_latch);
> /* Signal here to make sure the pmd finishes
> @@ -4481,6 +4515,7 @@ dp_netdev_add_port_tx_to_pmd(struct
>dp_netdev_pmd_thread *pmd,
>
> tx->port = port;
> tx->qid = -1;
> + tx->last_used_qid = LAST_USED_QID_NONE;
>
> hmap_insert(&pmd->tx_ports, &tx->node, hash_port_no(tx->port-
>>port_no));
> pmd->need_reload = true;
> @@ -5051,6 +5086,14 @@ dpif_netdev_xps_get_tx_qid(const struct
>dp_netdev_pmd_thread *pmd,
>
> dpif_netdev_xps_revalidate_pmd(pmd, now, false);
>
> + /* The tx queue can change in XPS case, make sure packets in
previous
> + * queue is flushed properly. */
> + if (tx->last_used_qid != LAST_USED_QID_NONE &&
> + tx->qid != tx->last_used_qid) {
> + netdev_txq_flush(port->netdev, tx->last_used_qid, port-
>>dynamic_txqs);
> + tx->last_used_qid = LAST_USED_QID_NONE;
> + }
> +
> VLOG_DBG("Core %d: New TX queue ID %d for port \'%s\'.",
> pmd->core_id, tx->qid,
netdev_get_name(tx->port->netdev));
> return min_qid;
> @@ -5146,6 +5189,13 @@ dp_execute_cb(void *aux_, struct
>dp_packet_batch *packets_,
> tx_qid = pmd->static_tx_qid;
> }
>
> + /* In case these packets gets buffered into an
intermediate
> + * queue and XPS is enabled the flush function could find
a
> + * different tx qid assigned to its thread. We keep track
> + * of the qid we're now using, that will trigger the flush
> + * function and will select the right queue to flush. */
> + p->last_used_qid = tx_qid;
> +
> netdev_send(p->port->netdev, tx_qid, packets_, may_steal,
> dynamic_txqs);
> return;
> --
> 2.4.11
>
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