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Zebra fpm backpressure #16220

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merged 4 commits into from
Sep 6, 2024
+146 −50
Merged

Zebra fpm backpressure #16220

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34670c4
zebra: Use the ctx queue counters
donaldsharp Jun 17, 2024
3af381b
zebra: Modify dplane loop to allow backpressure to filter up
donaldsharp Jun 12, 2024
8926ac1
zebra: Limit queue depth in dplane_fpm_nl
donaldsharp Jun 12, 2024
98b11de
zebra: Modify show `zebra dplane providers` to give more data
donaldsharp Jun 17, 2024
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19 changes: 19 additions & 0 deletions zebra/dplane_fpm_nl.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1678,6 +1678,25 @@ static int fpm_nl_process(struct zebra_dplane_provider *prov)

fnc = dplane_provider_get_data(prov);
limit = dplane_provider_get_work_limit(prov);

frr_with_mutex (&fnc->ctxqueue_mutex) {
cur_queue = dplane_ctx_queue_count(&fnc->ctxqueue);
}

if (cur_queue >= (uint64_t)limit) {
if (IS_ZEBRA_DEBUG_FPM)
zlog_debug("%s: Already at a limit(%" PRIu64
") of internal work, hold off",
__func__, cur_queue);
limit = 0;
} else if (cur_queue != 0) {
if (IS_ZEBRA_DEBUG_FPM)
zlog_debug("%s: current queue is %" PRIu64
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", limiting to lesser amount of %" PRIu64,
__func__, cur_queue, limit - cur_queue);
limit -= cur_queue;
}

for (counter = 0; counter < limit; counter++) {
ctx = dplane_provider_dequeue_in_ctx(prov);
if (ctx == NULL)
Expand Down
1 change: 1 addition & 0 deletions zebra/rib.h
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Original file line number Diff line number Diff line change
Expand Up @@ -631,6 +631,7 @@ extern int rib_add_gr_run(afi_t afi, vrf_id_t vrf_id, uint8_t proto,
uint8_t instance, time_t restart_time);

extern void zebra_vty_init(void);
extern uint32_t zebra_rib_dplane_results_count(void);

extern pid_t pid;

Expand Down
165 changes: 115 additions & 50 deletions zebra/zebra_dplane.c
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Original file line number Diff line number Diff line change
Expand Up @@ -483,10 +483,8 @@ struct zebra_dplane_provider {
int (*dp_fini)(struct zebra_dplane_provider *prov, bool early_p);

_Atomic uint32_t dp_in_counter;
_Atomic uint32_t dp_in_queued;
_Atomic uint32_t dp_in_max;
_Atomic uint32_t dp_out_counter;
_Atomic uint32_t dp_out_queued;
_Atomic uint32_t dp_out_max;
_Atomic uint32_t dp_error_counter;

Expand Down Expand Up @@ -6129,35 +6127,45 @@ int dplane_show_provs_helper(struct vty *vty, bool detailed)
struct zebra_dplane_provider *prov;
uint64_t in, in_q, in_max, out, out_q, out_max;

vty_out(vty, "Zebra dataplane providers:\n");

DPLANE_LOCK();
prov = dplane_prov_list_first(&zdplane_info.dg_providers);
in = dplane_ctx_queue_count(&zdplane_info.dg_update_list);
DPLANE_UNLOCK();

vty_out(vty, "dataplane Incoming Queue from Zebra: %" PRIu64 "\n", in);
vty_out(vty, "Zebra dataplane providers:\n");

/* Show counters, useful info from each registered provider */
while (prov) {
dplane_provider_lock(prov);
in_q = dplane_ctx_queue_count(&prov->dp_ctx_in_list);
out_q = dplane_ctx_queue_count(&prov->dp_ctx_out_list);
dplane_provider_unlock(prov);

in = atomic_load_explicit(&prov->dp_in_counter,
memory_order_relaxed);
in_q = atomic_load_explicit(&prov->dp_in_queued,
memory_order_relaxed);

in_max = atomic_load_explicit(&prov->dp_in_max,
memory_order_relaxed);
out = atomic_load_explicit(&prov->dp_out_counter,
memory_order_relaxed);
out_q = atomic_load_explicit(&prov->dp_out_queued,
memory_order_relaxed);

out_max = atomic_load_explicit(&prov->dp_out_max,
memory_order_relaxed);

vty_out(vty, "%s (%u): in: %"PRIu64", q: %"PRIu64", q_max: %"PRIu64", out: %"PRIu64", q: %"PRIu64", q_max: %"PRIu64"\n",
prov->dp_name, prov->dp_id, in, in_q, in_max,
out, out_q, out_max);
vty_out(vty,
" %s (%u): in: %" PRIu64 ", q: %" PRIu64
", q_max: %" PRIu64 ", out: %" PRIu64 ", q: %" PRIu64
", q_max: %" PRIu64 "\n",
prov->dp_name, prov->dp_id, in, in_q, in_max, out,
out_q, out_max);

prov = dplane_prov_list_next(&zdplane_info.dg_providers, prov);
}

out = zebra_rib_dplane_results_count();
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vty_out(vty, "dataplane Outgoing Queue to Zebra: %" PRIu64 "\n", out);

return CMD_SUCCESS;
}

Expand Down Expand Up @@ -6299,10 +6307,6 @@ struct zebra_dplane_ctx *dplane_provider_dequeue_in_ctx(
dplane_provider_lock(prov);

ctx = dplane_ctx_list_pop(&(prov->dp_ctx_in_list));
if (ctx) {
atomic_fetch_sub_explicit(&prov->dp_in_queued, 1,
memory_order_relaxed);
}

dplane_provider_unlock(prov);

Expand Down Expand Up @@ -6330,10 +6334,6 @@ int dplane_provider_dequeue_in_list(struct zebra_dplane_provider *prov,
break;
}

if (ret > 0)
atomic_fetch_sub_explicit(&prov->dp_in_queued, ret,
memory_order_relaxed);

dplane_provider_unlock(prov);

return ret;
Expand All @@ -6358,10 +6358,7 @@ void dplane_provider_enqueue_out_ctx(struct zebra_dplane_provider *prov,
dplane_ctx_list_add_tail(&(prov->dp_ctx_out_list), ctx);

/* Maintain out-queue counters */
atomic_fetch_add_explicit(&(prov->dp_out_queued), 1,
memory_order_relaxed);
curr = atomic_load_explicit(&prov->dp_out_queued,
memory_order_relaxed);
curr = dplane_ctx_queue_count(&prov->dp_ctx_out_list);
high = atomic_load_explicit(&prov->dp_out_max,
memory_order_relaxed);
if (curr > high)
Expand All @@ -6383,9 +6380,6 @@ dplane_provider_dequeue_out_ctx(struct zebra_dplane_provider *prov)
if (!ctx)
return NULL;

atomic_fetch_sub_explicit(&(prov->dp_out_queued), 1,
memory_order_relaxed);

return ctx;
}

Expand Down Expand Up @@ -7331,10 +7325,10 @@ static void dplane_thread_loop(struct event *event)
{
struct dplane_ctx_list_head work_list;
struct dplane_ctx_list_head error_list;
struct zebra_dplane_provider *prov;
struct zebra_dplane_provider *prov, *next_prov;
struct zebra_dplane_ctx *ctx;
int limit, counter, error_counter;
uint64_t curr, high;
uint64_t curr, out_curr, high;
bool reschedule = false;

/* Capture work limit per cycle */
Expand All @@ -7358,18 +7352,48 @@ static void dplane_thread_loop(struct event *event)
/* Locate initial registered provider */
prov = dplane_prov_list_first(&zdplane_info.dg_providers);

/* Move new work from incoming list to temp list */
for (counter = 0; counter < limit; counter++) {
ctx = dplane_ctx_list_pop(&zdplane_info.dg_update_list);
if (ctx) {
ctx->zd_provider = prov->dp_id;
curr = dplane_ctx_queue_count(&prov->dp_ctx_in_list);
out_curr = dplane_ctx_queue_count(&prov->dp_ctx_out_list);

dplane_ctx_list_add_tail(&work_list, ctx);
} else {
break;
if (curr >= (uint64_t)limit) {
if (IS_ZEBRA_DEBUG_DPLANE_DETAIL)
zlog_debug("%s: Current first provider(%s) Input queue is %" PRIu64
", holding off work",
__func__, prov->dp_name, curr);
counter = 0;
} else if (out_curr >= (uint64_t)limit) {
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Can it be a situation where the input and output queue is hitting the limit?

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Yeah but it doesn't matter from my perspective. Both cases we do the same thing. It's sufficient to just state the first one encountered in a debug and move on.

if (IS_ZEBRA_DEBUG_DPLANE_DETAIL)
zlog_debug("%s: Current first provider(%s) Output queue is %" PRIu64
", holding off work",
__func__, prov->dp_name, out_curr);
counter = 0;
} else {
int tlimit;
/*
* Let's limit the work to how what can be put on the
* in or out queue without going over
*/
tlimit = limit - MAX(curr, out_curr);
/* Move new work from incoming list to temp list */
for (counter = 0; counter < tlimit; counter++) {
ctx = dplane_ctx_list_pop(&zdplane_info.dg_update_list);
if (ctx) {
ctx->zd_provider = prov->dp_id;

dplane_ctx_list_add_tail(&work_list, ctx);
} else {
break;
}
}
}

/*
* If there is anything still on the two input queues reschedule
*/
if (dplane_ctx_queue_count(&prov->dp_ctx_in_list) > 0 ||
dplane_ctx_queue_count(&zdplane_info.dg_update_list) > 0)
reschedule = true;

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Can we drop this change?

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err. I intentionally added a newline to space things out a bit. So I am a bit confused

DPLANE_UNLOCK();

atomic_fetch_sub_explicit(&zdplane_info.dg_routes_queued, counter,
Expand All @@ -7388,8 +7412,9 @@ static void dplane_thread_loop(struct event *event)
* items.
*/
if (IS_ZEBRA_DEBUG_DPLANE_DETAIL)
zlog_debug("dplane enqueues %d new work to provider '%s'",
counter, dplane_provider_get_name(prov));
zlog_debug("dplane enqueues %d new work to provider '%s' curr is %" PRIu64,
counter, dplane_provider_get_name(prov),
curr);

/* Capture current provider id in each context; check for
* error status.
Expand Down Expand Up @@ -7422,10 +7447,7 @@ static void dplane_thread_loop(struct event *event)

atomic_fetch_add_explicit(&prov->dp_in_counter, counter,
memory_order_relaxed);
atomic_fetch_add_explicit(&prov->dp_in_queued, counter,
memory_order_relaxed);
curr = atomic_load_explicit(&prov->dp_in_queued,
memory_order_relaxed);
curr = dplane_ctx_queue_count(&prov->dp_ctx_in_list);
high = atomic_load_explicit(&prov->dp_in_max,
memory_order_relaxed);
if (curr > high)
Expand All @@ -7450,18 +7472,61 @@ static void dplane_thread_loop(struct event *event)
if (!zdplane_info.dg_run)
break;

/* Locate next provider */
next_prov = dplane_prov_list_next(&zdplane_info.dg_providers,
prov);
if (next_prov) {
curr = dplane_ctx_queue_count(
&next_prov->dp_ctx_in_list);
out_curr = dplane_ctx_queue_count(
&next_prov->dp_ctx_out_list);
} else
out_curr = curr = 0;

/* Dequeue completed work from the provider */
dplane_provider_lock(prov);

while (counter < limit) {
ctx = dplane_provider_dequeue_out_ctx(prov);
if (ctx) {
dplane_ctx_list_add_tail(&work_list, ctx);
counter++;
} else
break;
if (curr >= (uint64_t)limit) {
if (IS_ZEBRA_DEBUG_DPLANE_DETAIL)
zlog_debug("%s: Next Provider(%s) Input queue is %" PRIu64
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IMO, printing next_prov->dp_name would be useful here, otherwise hard to distinguish?

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we are printing it?

", holding off work",
__func__, next_prov->dp_name, curr);
counter = 0;
} else if (out_curr >= (uint64_t)limit) {
if (IS_ZEBRA_DEBUG_DPLANE_DETAIL)
zlog_debug("%s: Next Provider(%s) Output queue is %" PRIu64
", holding off work",
__func__, next_prov->dp_name,
out_curr);
counter = 0;
} else {
int tlimit;

/*
* Let's limit the work to how what can be put on the
* in or out queue without going over
*/
tlimit = limit - MAX(curr, out_curr);
while (counter < tlimit) {
ctx = dplane_provider_dequeue_out_ctx(prov);
if (ctx) {
dplane_ctx_list_add_tail(&work_list,
ctx);
counter++;
} else
break;
}
}

/*
* Let's check if there are still any items on the
* input or output queus of the current provider
* if so then we know we need to reschedule.
*/
if (dplane_ctx_queue_count(&prov->dp_ctx_in_list) > 0 ||
dplane_ctx_queue_count(&prov->dp_ctx_out_list) > 0)
reschedule = true;

dplane_provider_unlock(prov);

if (counter >= limit)
Expand All @@ -7477,7 +7542,7 @@ static void dplane_thread_loop(struct event *event)
}

/* Locate next provider */
prov = dplane_prov_list_next(&zdplane_info.dg_providers, prov);
prov = next_prov;
}

/*
Expand Down
11 changes: 11 additions & 0 deletions zebra/zebra_rib.c
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Expand Up @@ -5108,6 +5108,17 @@ static int rib_dplane_results(struct dplane_ctx_list_head *ctxlist)
return 0;
}

uint32_t zebra_rib_dplane_results_count(void)
{
uint32_t count;

frr_with_mutex (&dplane_mutex) {
count = dplane_ctx_queue_count(&rib_dplane_q);
}

return count;
}

/*
* Ensure there are no empty slots in the route_info array.
* Every route type in zebra should be present there.
Expand Down
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