On 2/27/23 15:58, Eelco Chaudron wrote:
> Depending on the driver implementation, it can take from 0.2 seconds
> up to 2 seconds before offloaded flow statistics are updated. This is
> true for both TC and rte_flow-based offloading. This is causing a
> problem with min-revalidate-pps, as old statistic values are used
> during this period.
>
> This fix will wait for at least 2 seconds, by default, before assuming no
> packets where received during this period.
>
> Reviewed-by: Simon Horman <[email protected]>
> Signed-off-by: Eelco Chaudron <[email protected]>
> ---
>
> Changes:
> - v2: Use existing ukey->offloaded so the revalidate_missed_dp_flow case is
> also covered.
> - v3: Added OVS_REQUIRES(ukey->mutex) to should_revalidate() to keep
> thread-safety-analysis happy.
> - v4: Add a configurable option.
> After looking at multiple vendor implementation for both TC and
> rte_flow I came to the conclusion that the delay is roughly between
> 0.2 and 2 seconds. Updated commit message.
> - v5: Rebased to latest upstream master.
> Made the key parameter const in should_revalidate().
>
> ofproto/ofproto-dpif-upcall.c | 26 ++++++++++++++++----------
> ofproto/ofproto-provider.h | 4 ++++
> ofproto/ofproto.c | 9 +++++++++
> ofproto/ofproto.h | 2 ++
> vswitchd/bridge.c | 3 +++
> vswitchd/vswitch.xml | 12 ++++++++++++
> 6 files changed, 46 insertions(+), 10 deletions(-)
>
> diff --git a/ofproto/ofproto-dpif-upcall.c b/ofproto/ofproto-dpif-upcall.c
> index fc94078cb..60c273a1d 100644
> --- a/ofproto/ofproto-dpif-upcall.c
> +++ b/ofproto/ofproto-dpif-upcall.c
> @@ -2100,10 +2100,12 @@ ukey_delete(struct umap *umap, struct udpif_key *ukey)
> }
>
> static bool
> -should_revalidate(const struct udpif *udpif, uint64_t packets,
> - long long int used)
> +should_revalidate(const struct udpif *udpif, const struct udpif_key *ukey,
> + uint64_t packets)
> + OVS_REQUIRES(ukey->mutex)
> {
> long long int metric, now, duration;
> + long long int used = ukey->stats.used;
>
> if (!ofproto_min_revalidate_pps) {
> return true;
> @@ -2134,8 +2136,12 @@ should_revalidate(const struct udpif *udpif, uint64_t
> packets,
> duration = now - used;
> metric = duration / packets;
>
> - if (metric < 1000 / ofproto_min_revalidate_pps) {
> - /* The flow is receiving more than min-revalidate-pps, so keep it. */
> + if (metric < 1000 / ofproto_min_revalidate_pps ||
> + (ukey->offloaded && duration < ofproto_offloaded_stats_delay)) {
> + /* The flow is receiving more than min-revalidate-pps, so keep it.
> + * Or it's a hardware offloaded flow that might take up to X seconds
> + * to update its statistics. Until we are sure the statistics had a
> + * chance to be updated, also keep it. */
> return true;
> }
> return false;
> @@ -2339,7 +2345,7 @@ static enum reval_result
> revalidate_ukey(struct udpif *udpif, struct udpif_key *ukey,
> const struct dpif_flow_stats *stats,
> struct ofpbuf *odp_actions, uint64_t reval_seq,
> - struct recirc_refs *recircs, bool offloaded)
> + struct recirc_refs *recircs)
> OVS_REQUIRES(ukey->mutex)
> {
> bool need_revalidate = ukey->reval_seq != reval_seq;
> @@ -2358,7 +2364,7 @@ revalidate_ukey(struct udpif *udpif, struct udpif_key
> *ukey,
> : 0);
>
> if (need_revalidate) {
> - if (should_revalidate(udpif, push.n_packets, ukey->stats.used)) {
> + if (should_revalidate(udpif, ukey, push.n_packets)) {
> if (!ukey->xcache) {
> ukey->xcache = xlate_cache_new();
> } else {
> @@ -2374,7 +2380,7 @@ revalidate_ukey(struct udpif *udpif, struct udpif_key
> *ukey,
>
> /* Stats for deleted flows will be attributed upon flow deletion. Skip.
> */
> if (result != UKEY_DELETE) {
> - xlate_push_stats(ukey->xcache, &push, offloaded);
> + xlate_push_stats(ukey->xcache, &push, ukey->offloaded);
> ukey->stats = *stats;
> ukey->reval_seq = reval_seq;
> }
> @@ -2774,6 +2780,7 @@ revalidate(struct revalidator *revalidator)
> continue;
> }
>
> + ukey->offloaded = f->attrs.offloaded;
> already_dumped = ukey->dump_seq == dump_seq;
> if (already_dumped) {
> /* The flow has already been handled during this flow dump
> @@ -2805,8 +2812,7 @@ revalidate(struct revalidator *revalidator)
> result = UKEY_DELETE;
> } else {
> result = revalidate_ukey(udpif, ukey, &stats, &odp_actions,
> - reval_seq, &recircs,
> - f->attrs.offloaded);
> + reval_seq, &recircs);
> }
> ukey->dump_seq = dump_seq;
>
> @@ -2891,7 +2897,7 @@ revalidator_sweep__(struct revalidator *revalidator,
> bool purge)
> COVERAGE_INC(revalidate_missed_dp_flow);
> memcpy(&stats, &ukey->stats, sizeof stats);
> result = revalidate_ukey(udpif, ukey, &stats,
> &odp_actions,
> - reval_seq, &recircs, false);
> + reval_seq, &recircs);
> }
> if (result != UKEY_KEEP) {
> /* Clears 'recircs' if filled by revalidate_ukey(). */
> diff --git a/ofproto/ofproto-provider.h b/ofproto/ofproto-provider.h
> index a84ddc1d0..71341a01f 100644
> --- a/ofproto/ofproto-provider.h
> +++ b/ofproto/ofproto-provider.h
> @@ -541,6 +541,10 @@ extern unsigned ofproto_max_revalidator;
> * duration exceeds half of max-revalidator config variable. */
> extern unsigned ofproto_min_revalidate_pps;
>
> +/* Worst case delay (in ms) it might take before statistics of offloaded
> flows
> + * are updated. This is used when calculating the min revalidate pps. */
This comment is confusing, because 'min revalidate pps' is a configuration
option and we do not calculate it. We should say 'Offloaded flows younger
than this delay will always be revalidated regardless of
ofproto_min_revalidate_pps'.
Or something along these lines.
> +extern unsigned ofproto_offloaded_stats_delay;
> +
> /* Number of upcall handler and revalidator threads. Only affects the
> * ofproto-dpif implementation. */
> extern uint32_t n_handlers, n_revalidators;
> diff --git a/ofproto/ofproto.c b/ofproto/ofproto.c
> index 863b34d25..69fece4c5 100644
> --- a/ofproto/ofproto.c
> +++ b/ofproto/ofproto.c
> @@ -311,6 +311,7 @@ unsigned ofproto_flow_limit = OFPROTO_FLOW_LIMIT_DEFAULT;
> unsigned ofproto_max_idle = OFPROTO_MAX_IDLE_DEFAULT;
> unsigned ofproto_max_revalidator = OFPROTO_MAX_REVALIDATOR_DEFAULT;
> unsigned ofproto_min_revalidate_pps = OFPROTO_MIN_REVALIDATE_PPS_DEFAULT;
> +unsigned ofproto_offloaded_stats_delay = OFPROTO_OFFLOADED_STATS_DELAY;
>
> uint32_t n_handlers, n_revalidators;
>
> @@ -727,6 +728,14 @@ ofproto_set_min_revalidate_pps(unsigned
> min_revalidate_pps)
> ofproto_min_revalidate_pps = min_revalidate_pps;
> }
>
> +/* Set worst case delay (in ms) it might take before statistics of offloaded
> + * flows are updated. This is used when calculating the min revalidate pps.
> */
Same here.
> +void
> +ofproto_set_offloaded_stats_delay(unsigned offloaded_stats_delay)
> +{
> + ofproto_offloaded_stats_delay = offloaded_stats_delay;
> +}
> +
> /* If forward_bpdu is true, the NORMAL action will forward frames with
> * reserved (e.g. STP) destination Ethernet addresses. if forward_bpdu is
> false,
> * the NORMAL action will drop these frames. */
> diff --git a/ofproto/ofproto.h b/ofproto/ofproto.h
> index 4e15167ab..fa7973ac7 100644
> --- a/ofproto/ofproto.h
> +++ b/ofproto/ofproto.h
> @@ -311,6 +311,7 @@ int ofproto_port_dump_done(struct ofproto_port_dump *);
> #define OFPROTO_MAX_IDLE_DEFAULT 10000 /* ms */
> #define OFPROTO_MAX_REVALIDATOR_DEFAULT 500 /* ms */
> #define OFPROTO_MIN_REVALIDATE_PPS_DEFAULT 5
> +#define OFPROTO_OFFLOADED_STATS_DELAY 2000 /* ms */
>
> const char *ofproto_port_open_type(const struct ofproto *,
> const char *port_type);
> @@ -340,6 +341,7 @@ void ofproto_set_flow_limit(unsigned limit);
> void ofproto_set_max_idle(unsigned max_idle);
> void ofproto_set_max_revalidator(unsigned max_revalidator);
> void ofproto_set_min_revalidate_pps(unsigned min_revalidate_pps);
> +void ofproto_set_offloaded_stats_delay(unsigned offloaded_stats_delay);
> void ofproto_set_forward_bpdu(struct ofproto *, bool forward_bpdu);
> void ofproto_set_mac_table_config(struct ofproto *, unsigned idle_time,
> size_t max_entries);
> diff --git a/vswitchd/bridge.c b/vswitchd/bridge.c
> index abf2afe57..c35c16c8d 100644
> --- a/vswitchd/bridge.c
> +++ b/vswitchd/bridge.c
> @@ -832,6 +832,9 @@ bridge_reconfigure(const struct ovsrec_open_vswitch
> *ovs_cfg)
> ofproto_set_min_revalidate_pps(
> smap_get_uint(&ovs_cfg->other_config, "min-revalidate-pps",
> OFPROTO_MIN_REVALIDATE_PPS_DEFAULT));
> + ofproto_set_offloaded_stats_delay(
> + smap_get_uint(&ovs_cfg->other_config, "offloaded-stats-delay",
> + OFPROTO_OFFLOADED_STATS_DELAY));
> ofproto_set_vlan_limit(smap_get_int(&ovs_cfg->other_config, "vlan-limit",
> LEGACY_MAX_VLAN_HEADERS));
> ofproto_set_bundle_idle_timeout(smap_get_uint(&ovs_cfg->other_config,
> diff --git a/vswitchd/vswitch.xml b/vswitchd/vswitch.xml
> index 05ac1fbe5..fde19838d 100644
> --- a/vswitchd/vswitch.xml
> +++ b/vswitchd/vswitch.xml
> @@ -216,6 +216,18 @@
> </p>
> </column>
>
> + <column name="other_config" key="offloaded-stats-delay"
> + type='{"type": "integer", "minInteger": 0}'>
> + <p>
> + Set worst case delay (in ms) it might take before statistics of
> + offloaded flows are updated. This is used when calculating the
> + min-revalidate-pps.
Same here.
Nit: Please use xml markup to refer options. i.e.:
<ref column="other_config" key="min-revalidate-pps"/>
Would still be great if we didn't need this patch at all,
but I guess we stuck with it for now.
Best regards, Ilya Maximets.
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