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tcp: Make hostcache.cache_count MPSAFE by using a counter_u64_t

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Addressing the underlying root cause for cache_count to
show unexpectedly high  values, by protecting all arithmetic on
that global variable by using counter(9).

PR:		254333
Reviewed By: tuexen, #transport
MFC after: 2 weeks
Sponsored by: NetApp, Inc.
Differential Revision: https://reviews.freebsd.org/D29510
This commit is contained in:
Richard Scheffenegger 2021-03-31 19:30:20 +02:00
parent 5394893269
commit 95e56d31e3
2 changed files with 22 additions and 18 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

20
sys/netinet/tcp_hostcache.c
View file

@ -147,8 +147,8 @@ SYSCTL_UINT(_net_inet_tcp_hostcache, OID_AUTO, bucketlimit,
CTLFLAG_VNET | CTLFLAG_RDTUN, &VNET_NAME(tcp_hostcache.bucket_limit), 0,
"Per-bucket hash limit for hostcache");
SYSCTL_UINT(_net_inet_tcp_hostcache, OID_AUTO, count, CTLFLAG_VNET | CTLFLAG_RD,
&VNET_NAME(tcp_hostcache.cache_count), 0,
SYSCTL_COUNTER_U64(_net_inet_tcp_hostcache, OID_AUTO, count, CTLFLAG_VNET | CTLFLAG_RD,
&VNET_NAME(tcp_hostcache.cache_count),
"Current number of entries in hostcache");
SYSCTL_INT(_net_inet_tcp_hostcache, OID_AUTO, expire, CTLFLAG_VNET | CTLFLAG_RW,
@ -199,7 +199,8 @@ tcp_hc_init(void)
/*
* Initialize hostcache structures.
*/
V_tcp_hostcache.cache_count = 0;
V_tcp_hostcache.cache_count = counter_u64_alloc(M_WAITOK);
counter_u64_zero(V_tcp_hostcache.cache_count);
V_tcp_hostcache.hashsize = TCP_HOSTCACHE_HASHSIZE;
V_tcp_hostcache.bucket_limit = TCP_HOSTCACHE_BUCKETLIMIT;
V_tcp_hostcache.expire = TCP_HOSTCACHE_EXPIRE;
@ -267,6 +268,9 @@ tcp_hc_destroy(void)
/* Purge all hc entries. */
tcp_hc_purge_internal(1);
/* Release the counter */
counter_u64_free(V_tcp_hostcache.cache_count);
/* Free the uma zone and the allocated hash table. */
uma_zdestroy(V_tcp_hostcache.zone);
@ -374,7 +378,7 @@ tcp_hc_insert(struct in_conninfo *inc)
* If the bucket limit is reached, reuse the least-used element.
*/
if (hc_head->hch_length >= V_tcp_hostcache.bucket_limit ||
V_tcp_hostcache.cache_count >= V_tcp_hostcache.cache_limit) {
counter_u64_fetch(V_tcp_hostcache.cache_count) >= V_tcp_hostcache.cache_limit) {
hc_entry = TAILQ_LAST(&hc_head->hch_bucket, hc_qhead);
/*
* At first we were dropping the last element, just to
@ -391,7 +395,7 @@ tcp_hc_insert(struct in_conninfo *inc)
}
TAILQ_REMOVE(&hc_head->hch_bucket, hc_entry, rmx_q);
V_tcp_hostcache.hashbase[hash].hch_length--;
V_tcp_hostcache.cache_count--;
counter_u64_add(V_tcp_hostcache.cache_count, -1);
TCPSTAT_INC(tcps_hc_bucketoverflow);
#if 0
uma_zfree(V_tcp_hostcache.zone, hc_entry);
@ -424,7 +428,7 @@ tcp_hc_insert(struct in_conninfo *inc)
*/
TAILQ_INSERT_HEAD(&hc_head->hch_bucket, hc_entry, rmx_q);
V_tcp_hostcache.hashbase[hash].hch_length++;
V_tcp_hostcache.cache_count++;
counter_u64_add(V_tcp_hostcache.cache_count, 1);
TCPSTAT_INC(tcps_hc_added);
return hc_entry;
@ -640,7 +644,7 @@ sysctl_tcp_hc_list(SYSCTL_HANDLER_ARGS)
/* Optimize Buffer length query by sbin/sysctl */
if (req->oldptr == NULL) {
len = (V_tcp_hostcache.cache_count + 1) * linesize;
len = (counter_u64_fetch(V_tcp_hostcache.cache_count) + 1) * linesize;
return (SYSCTL_OUT(req, NULL, len));
}
@ -712,7 +716,7 @@ tcp_hc_purge_internal(int all)
hc_entry, rmx_q);
uma_zfree(V_tcp_hostcache.zone, hc_entry);
V_tcp_hostcache.hashbase[i].hch_length--;
V_tcp_hostcache.cache_count--;
counter_u64_add(V_tcp_hostcache.cache_count, -1);
} else
hc_entry->rmx_expire -= V_tcp_hostcache.prune;
}

20
sys/netinet/tcp_hostcache.h
View file

@ -69,16 +69,16 @@ struct hc_metrics {
};
struct tcp_hostcache {
struct hc_head *hashbase;
uma_zone_t zone;
u_int hashsize;
u_int hashmask;
u_int bucket_limit;
u_int cache_count;
u_int cache_limit;
int expire;
int prune;
int purgeall;
struct hc_head *hashbase;
uma_zone_t zone;
u_int hashsize;
u_int hashmask;
u_int bucket_limit;
counter_u64_t cache_count;
u_int cache_limit;
int expire;
int prune;
int purgeall;
};
#endif /* !_NETINET_TCP_HOSTCACHE_H_*/