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ovn-controller dns-cache: Improve dns caching using cmaps.
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Its possible for pinctrl handling for DNS packets to be blocked
if the ovn-controller main thread has acquired the dns cache
mutex during the recompute.  This patch improves the DNS packet
handling by using cmap instead of hmap to maintain the dns cache.
With this, there is no need to maintain a mutex.

Since cmaps use OVSRCU_TYPE, in order to safely free the cmap data,
we need to manage the quiesce state for both the main ovn-controller
thread and pinctrl thread.  ovsrcu_quiesce_start() is called before
calling poll_block() and ovsrcu_quiesce_end() is called at the
start of the while for both these threads.

Suggested-by: Ales Musil <amusil@redhat.com>
Acked-by: Ales Musil <amusil@redhat.com>
Signed-off-by: Numan Siddique <numans@ovn.org>
(cherry picked from commit eba60b2)
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@numansiddique
numansiddique committed Jan 15, 2025
1 parent 299b503 commit 5d3a4e0
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Showing 3 changed files with 67 additions and 84 deletions.
3 changes: 3 additions & 0 deletions controller/ovn-controller.c
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Original file line number Diff line number Diff line change
Expand Up @@ -5376,6 +5376,8 @@ main(int argc, char *argv[])
/* Main loop. */
bool sb_monitor_all = false;
while (!exit_args.exiting) {
ovsrcu_quiesce_end();

memory_run();
if (memory_should_report()) {
struct simap usage = SIMAP_INITIALIZER(&usage);
Expand Down Expand Up @@ -5863,6 +5865,7 @@ main(int argc, char *argv[])

loop_done:
memory_wait();
ovsrcu_quiesce_start();
poll_block();
if (should_service_stop()) {
exit_args.exiting = true;
Expand Down
144 changes: 60 additions & 84 deletions controller/ovn-dns.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@
/* OVS includes */
#include "include/openvswitch/shash.h"
#include "include/openvswitch/thread.h"
#include "lib/cmap.h"
#include "openvswitch/vlog.h"

/* OVN includes. */
Expand All @@ -28,7 +29,7 @@ VLOG_DEFINE_THIS_MODULE(ovndns);

/* Internal DNS cache entry for each SB DNS record. */
struct dns_data {
struct hmap_node hmap_node;
struct cmap_node cmap_node;
struct uuid uuid;
uint64_t *dps;
size_t n_dps;
Expand All @@ -38,114 +39,87 @@ struct dns_data {
};

/* shash of 'struct dns_data'. */
static struct hmap dns_cache_ = HMAP_INITIALIZER(&dns_cache_);

/* Mutex to protect dns_cache_. */
static struct ovs_mutex dns_cache_mutex = OVS_MUTEX_INITIALIZER;
static struct cmap dns_cache_;

static void update_cache_with_dns_rec(const struct sbrec_dns *,
struct dns_data *,
const struct uuid *uuid,
struct hmap *dns_cache);
static struct dns_data *dns_data_find(const struct uuid *uuid);
struct cmap *dns_cache);
static struct dns_data *dns_data_find(const struct uuid *uuid,
const struct cmap *);
static struct dns_data *dns_data_alloc(struct uuid uuid);
static void dns_data_destroy(struct dns_data *dns_data);
static void destroy_dns_cache(struct cmap *dns_cache);

void
ovn_dns_cache_init(void)
{
cmap_init(&dns_cache_);
}

void
ovn_dns_cache_destroy(void)
{
ovs_mutex_lock(&dns_cache_mutex);
struct dns_data *dns_data;
HMAP_FOR_EACH_POP (dns_data, hmap_node, &dns_cache_) {
dns_data_destroy(dns_data);
}
hmap_destroy(&dns_cache_);
ovs_mutex_unlock(&dns_cache_mutex);
destroy_dns_cache(&dns_cache_);
cmap_destroy(&dns_cache_);
}

void
ovn_dns_sync_cache(const struct sbrec_dns_table *dns_table)
{
ovs_mutex_lock(&dns_cache_mutex);
struct dns_data *dns_data;
HMAP_FOR_EACH (dns_data, hmap_node, &dns_cache_) {
dns_data->delete = true;
const struct sbrec_dns *sbrec_dns;
struct dns_data *existing;

CMAP_FOR_EACH (existing, cmap_node, &dns_cache_) {
existing->delete = true;
}

const struct sbrec_dns *sbrec_dns;
SBREC_DNS_TABLE_FOR_EACH (sbrec_dns, dns_table) {
const struct uuid *uuid = &sbrec_dns->header_.uuid;
dns_data = dns_data_find(uuid);
if (!dns_data) {
dns_data = dns_data_alloc(*uuid);
hmap_insert(&dns_cache_, &dns_data->hmap_node, uuid_hash(uuid));
} else {
free(dns_data->dps);
}

dns_data->delete = false;

if (!smap_equal(&dns_data->records, &sbrec_dns->records)) {
smap_destroy(&dns_data->records);
smap_clone(&dns_data->records, &sbrec_dns->records);
}

if (!smap_equal(&dns_data->options, &sbrec_dns->options)) {
smap_destroy(&dns_data->options);
smap_clone(&dns_data->options, &sbrec_dns->options);
}

dns_data->n_dps = sbrec_dns->n_datapaths;
dns_data->dps = xcalloc(dns_data->n_dps, sizeof(uint64_t));
for (size_t i = 0; i < sbrec_dns->n_datapaths; i++) {
dns_data->dps[i] = sbrec_dns->datapaths[i]->tunnel_key;
}
existing = dns_data_find(uuid, &dns_cache_);
update_cache_with_dns_rec(sbrec_dns, existing, uuid,
&dns_cache_);
}

HMAP_FOR_EACH_SAFE (dns_data, hmap_node, &dns_cache_) {
if (dns_data->delete) {
hmap_remove(&dns_cache_, &dns_data->hmap_node);
dns_data_destroy(dns_data);
CMAP_FOR_EACH (existing, cmap_node, &dns_cache_) {
if (existing->delete) {
cmap_remove(&dns_cache_, &existing->cmap_node,
uuid_hash(&existing->uuid));
ovsrcu_postpone(dns_data_destroy, existing);
}
}
ovs_mutex_unlock(&dns_cache_mutex);
}

void
ovn_dns_update_cache(const struct sbrec_dns_table *dns_table)
{
ovs_mutex_lock(&dns_cache_mutex);

const struct sbrec_dns *sbrec_dns;
struct dns_data *existing;

SBREC_DNS_TABLE_FOR_EACH_TRACKED (sbrec_dns, dns_table) {
const struct uuid *uuid = &sbrec_dns->header_.uuid;
struct dns_data *dns_data = dns_data_find(uuid);

if (sbrec_dns_is_deleted(sbrec_dns) && dns_data) {
hmap_remove(&dns_cache_, &dns_data->hmap_node);
dns_data_destroy(dns_data);
existing = dns_data_find(uuid, &dns_cache_);
if (sbrec_dns_is_deleted(sbrec_dns) && existing) {
cmap_remove(&dns_cache_, &existing->cmap_node,
uuid_hash(&existing->uuid));
ovsrcu_postpone(dns_data_destroy, existing);
} else {
update_cache_with_dns_rec(sbrec_dns, dns_data, uuid, &dns_cache_);
update_cache_with_dns_rec(sbrec_dns, existing, uuid,
&dns_cache_);
}
}

ovs_mutex_unlock(&dns_cache_mutex);
}

const char *
ovn_dns_lookup(const char *query_name, uint64_t dp_key, bool *ovn_owned)
{
ovs_mutex_lock(&dns_cache_mutex);
const char *answer_data = NULL;
struct dns_data *dns_data;

*ovn_owned = false;
struct dns_data *dns_data;
const char *answer_data = NULL;
HMAP_FOR_EACH (dns_data, hmap_node, &dns_cache_) {

CMAP_FOR_EACH (dns_data, cmap_node, &dns_cache_) {
for (size_t i = 0; i < dns_data->n_dps; i++) {
if (dns_data->dps[i] == dp_key) {
/* DNS records in SBDB are stored in lowercase. Convert to
Expand All @@ -167,49 +141,42 @@ ovn_dns_lookup(const char *query_name, uint64_t dp_key, bool *ovn_owned)
}
}

ovs_mutex_unlock(&dns_cache_mutex);

return answer_data;
}


/* Static functions. */
static void
update_cache_with_dns_rec(const struct sbrec_dns *sbrec_dns,
struct dns_data *dns_data,
struct dns_data *existing,
const struct uuid *uuid,
struct hmap *dns_cache)
struct cmap *dns_cache)
{
if (!dns_data) {
dns_data = dns_data_alloc(*uuid);
hmap_insert(dns_cache, &dns_data->hmap_node, uuid_hash(uuid));
} else {
free(dns_data->dps);
}

if (!smap_equal(&dns_data->records, &sbrec_dns->records)) {
smap_destroy(&dns_data->records);
smap_clone(&dns_data->records, &sbrec_dns->records);
}

if (!smap_equal(&dns_data->options, &sbrec_dns->options)) {
smap_destroy(&dns_data->options);
smap_clone(&dns_data->options, &sbrec_dns->options);
}
struct dns_data *dns_data = dns_data_alloc(*uuid);
smap_clone(&dns_data->records, &sbrec_dns->records);
smap_clone(&dns_data->options, &sbrec_dns->options);

dns_data->n_dps = sbrec_dns->n_datapaths;
dns_data->dps = xcalloc(dns_data->n_dps, sizeof(uint64_t));
for (size_t i = 0; i < sbrec_dns->n_datapaths; i++) {
dns_data->dps[i] = sbrec_dns->datapaths[i]->tunnel_key;
}

if (!existing) {
cmap_insert(dns_cache, &dns_data->cmap_node, uuid_hash(uuid));
} else {
cmap_replace(dns_cache, &existing->cmap_node, &dns_data->cmap_node,
uuid_hash(uuid));
ovsrcu_postpone(dns_data_destroy, existing);
}
}

static struct dns_data *
dns_data_find(const struct uuid *uuid)
dns_data_find(const struct uuid *uuid, const struct cmap *dns_cache)
{
struct dns_data *dns_data;
size_t hash = uuid_hash(uuid);
HMAP_FOR_EACH_WITH_HASH (dns_data, hmap_node, hash, &dns_cache_) {
CMAP_FOR_EACH_WITH_HASH (dns_data, cmap_node, hash, dns_cache) {
if (uuid_equals(&dns_data->uuid, uuid)) {
return dns_data;
}
Expand Down Expand Up @@ -240,3 +207,12 @@ dns_data_destroy(struct dns_data *dns_data)
free(dns_data->dps);
free(dns_data);
}

static void
destroy_dns_cache(struct cmap *dns_cache)
{
struct dns_data *dns_data;
CMAP_FOR_EACH (dns_data, cmap_node, dns_cache) {
ovsrcu_postpone(dns_data_destroy, dns_data);
}
}
4 changes: 4 additions & 0 deletions controller/pinctrl.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -3884,6 +3884,8 @@ pinctrl_handler(void *arg_)
static long long int send_prefixd_time = LLONG_MAX;

while (!latch_is_set(&pctrl->pinctrl_thread_exit)) {
ovsrcu_quiesce_end();

long long int bfd_time = LLONG_MAX;
bool lock_failed = false;

Expand Down Expand Up @@ -3957,6 +3959,8 @@ pinctrl_handler(void *arg_)

latch_wait(&pctrl->pinctrl_thread_exit);
}

ovsrcu_quiesce_start();
poll_block();
}

Expand Down

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