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tcp: Add hash histogram output and validate bucket length accounting

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Provide a histogram output to check, if the hashsize or
bucketlimit could be optimized. Also add some basic sanity
checks around the accounting of the hash utilization.

MFC after: 2 weeks
Reviewed By: tuexen, #transport
Sponsored by: NetApp, Inc.
Differential Revision: https://reviews.freebsd.org/D29506
This commit is contained in:
Richard Scheffenegger 2021-04-01 14:44:05 +02:00
parent 529a2a0f27
commit 02f26e98c7
1 changed files with 62 additions and 0 deletions
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62
sys/netinet/tcp_hostcache.c
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@ -121,6 +121,7 @@ VNET_DEFINE_STATIC(struct callout, tcp_hc_callout);
static struct hc_metrics *tcp_hc_lookup(struct in_conninfo *);
static struct hc_metrics *tcp_hc_insert(struct in_conninfo *);
static int sysctl_tcp_hc_list(SYSCTL_HANDLER_ARGS);
static int sysctl_tcp_hc_histo(SYSCTL_HANDLER_ARGS);
static int sysctl_tcp_hc_purgenow(SYSCTL_HANDLER_ARGS);
static void tcp_hc_purge_internal(int);
static void tcp_hc_purge(void *);
@ -168,6 +169,11 @@ SYSCTL_PROC(_net_inet_tcp_hostcache, OID_AUTO, list,
0, 0, sysctl_tcp_hc_list, "A",
"List of all hostcache entries");
SYSCTL_PROC(_net_inet_tcp_hostcache, OID_AUTO, histo,
CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_SKIP | CTLFLAG_MPSAFE,
0, 0, sysctl_tcp_hc_histo, "A",
"Print a histogram of hostcache hashbucket utilization");
SYSCTL_PROC(_net_inet_tcp_hostcache, OID_AUTO, purgenow,
CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE,
NULL, 0, sysctl_tcp_hc_purgenow, "I",
@ -390,6 +396,11 @@ tcp_hc_insert(struct in_conninfo *inc)
return NULL;
}
TAILQ_REMOVE(&hc_head->hch_bucket, hc_entry, rmx_q);
KASSERT(V_tcp_hostcache.hashbase[hash].hch_length > 0 &&
V_tcp_hostcache.hashbase[hash].hch_length <=
V_tcp_hostcache.bucket_limit,
("tcp_hostcache: bucket length range violated at %u: %u",
hash, V_tcp_hostcache.hashbase[hash].hch_length));
V_tcp_hostcache.hashbase[hash].hch_length--;
atomic_subtract_int(&V_tcp_hostcache.cache_count, 1);
TCPSTAT_INC(tcps_hc_bucketoverflow);
@ -424,6 +435,10 @@ 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++;
KASSERT(V_tcp_hostcache.hashbase[hash].hch_length <
V_tcp_hostcache.bucket_limit,
("tcp_hostcache: bucket length too high at %u: %u",
hash, V_tcp_hostcache.hashbase[hash].hch_length));
atomic_add_int(&V_tcp_hostcache.cache_count, 1);
TCPSTAT_INC(tcps_hc_added);
@ -696,6 +711,48 @@ sysctl_tcp_hc_list(SYSCTL_HANDLER_ARGS)
return(error);
}
/*
* Sysctl function: prints a histogram of the hostcache hashbucket
* utilization.
*/
static int
sysctl_tcp_hc_histo(SYSCTL_HANDLER_ARGS)
{
const int linesize = 50;
struct sbuf sb;
int i, error;
int *histo;
u_int hch_length;
if (jailed_without_vnet(curthread->td_ucred) != 0)
return (EPERM);
histo = (int *)malloc(sizeof(int) * (V_tcp_hostcache.bucket_limit + 1),
M_TEMP, M_NOWAIT|M_ZERO);
if (histo == NULL)
return(ENOMEM);
for (i = 0; i < V_tcp_hostcache.hashsize; i++) {
hch_length = V_tcp_hostcache.hashbase[i].hch_length;
KASSERT(hch_length <= V_tcp_hostcache.bucket_limit,
("tcp_hostcache: bucket limit exceeded at %u: %u",
i, hch_length));
histo[hch_length]++;
}
/* Use a buffer for 16 lines */
sbuf_new_for_sysctl(&sb, NULL, 16 * linesize, req);
sbuf_printf(&sb, "\nLength\tCount\n");
for (i = 0; i <= V_tcp_hostcache.bucket_limit; i++) {
sbuf_printf(&sb, "%u\t%u\n", i, histo[i]);
}
error = sbuf_finish(&sb);
sbuf_delete(&sb);
free(histo, M_TEMP);
return(error);
}
/*
* Caller has to make sure the curvnet is set properly.
*/
@ -709,6 +766,11 @@ tcp_hc_purge_internal(int all)
THC_LOCK(&V_tcp_hostcache.hashbase[i].hch_mtx);
TAILQ_FOREACH_SAFE(hc_entry,
&V_tcp_hostcache.hashbase[i].hch_bucket, rmx_q, hc_next) {
KASSERT(V_tcp_hostcache.hashbase[i].hch_length > 0 &&
V_tcp_hostcache.hashbase[i].hch_length <=
V_tcp_hostcache.bucket_limit,
("tcp_hostcache: bucket langth out of range at %u: %u",
i, V_tcp_hostcache.hashbase[i].hch_length));
if (all || hc_entry->rmx_expire <= 0) {
TAILQ_REMOVE(&V_tcp_hostcache.hashbase[i].hch_bucket,
hc_entry, rmx_q);