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Move persistent connections to thread specific lists

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Making the lists of persistent DCBs thread specific is both a bug fix and
a performance enhancement. There was a small window where a non-owner
thread could receive events for a DCB. By partitioning the DCBs into
thread specific lists, this is avoided by removing the possibility of DCBs
moving between threads.
This commit is contained in:
Markus Makela
2016-11-26 05:52:26 +02:00
parent bcbff604b0
commit 5aa791d16e
5 changed files with 44 additions and 42 deletions
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2
include/maxscale/dcb.h
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@ -368,7 +368,7 @@ int dcb_add_callback(DCB *, DCB_REASON, int (*)(struct dcb *, DCB_REASON, void *
int dcb_remove_callback(DCB *, DCB_REASON, int (*)(struct dcb *, DCB_REASON, void *), void *);
int dcb_isvalid(DCB *); /* Check the DCB is in the linked list */
int dcb_count_by_usage(DCB_USAGE); /* Return counts of DCBs */
int dcb_persistent_clean_count(DCB *, bool); /* Clean persistent and return count */
int dcb_persistent_clean_count(DCB *, int, bool); /* Clean persistent and return count */
void dcb_hangup_foreach (struct server* server);
size_t dcb_get_session_id(DCB* dcb);
bool dcb_get_ses_log_info(DCB* dcb, size_t* sesid, int* enabled_logs);

5
include/maxscale/server.h
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@ -110,8 +110,7 @@ typedef struct server
int depth; /**< Replication level in the tree */
long slaves[MAX_NUM_SLAVES]; /**< Slaves of this node */
bool master_err_is_logged; /*< If node failed, this indicates whether it is logged */
DCB *persistent; /**< List of unused persistent connections to the server */
SPINLOCK persistlock; /**< Lock for adjusting the persistent connections list */
DCB **persistent; /**< List of unused persistent connections to the server */
long persistpoolmax; /**< Maximum size of persistent connections pool */
long persistmaxtime; /**< Maximum number of seconds connection can live */
int persistmax; /**< Maximum pool size actually achieved since startup */
@ -272,7 +271,7 @@ extern void serverAddMonUser(SERVER *, char *, char *);
extern void serverAddParameter(SERVER *, char *, char *);
extern char *serverGetParameter(SERVER *, char *);
extern void server_update_credentials(SERVER *, char *, char *);
extern DCB *server_get_persistent(SERVER *, char *, const char *);
extern DCB *server_get_persistent(SERVER *, char *, const char *, int);
extern void server_update_address(SERVER *, char *);
extern void server_update_port(SERVER *, unsigned short);
extern RESULTSET *serverGetList();

19
server/core/dcb.c
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@ -646,7 +646,7 @@ dcb_connect(SERVER *server, SESSION *session, const char *protocol)
{
MXS_DEBUG("%lu [dcb_connect] Looking for persistent connection DCB "
"user %s protocol %s\n", pthread_self(), user, protocol);
dcb = server_get_persistent(server, user, protocol);
dcb = server_get_persistent(server, user, protocol, session->client_dcb->thread.id);
if (dcb)
{
/**
@ -1695,7 +1695,7 @@ dcb_maybe_add_persistent(DCB *dcb)
&& (dcb->server->status & SERVER_RUNNING)
&& !dcb->dcb_errhandle_called
&& !(dcb->flags & DCBF_HUNG)
&& (poolcount = dcb_persistent_clean_count(dcb, false)) < dcb->server->persistpoolmax)
&& (poolcount = dcb_persistent_clean_count(dcb, dcb->thread.id, false)) < dcb->server->persistpoolmax)
{
DCB_CALLBACK *loopcallback;
MXS_DEBUG("%lu [dcb_maybe_add_persistent] Adding DCB to persistent pool, user %s.\n",
@ -1724,10 +1724,8 @@ dcb_maybe_add_persistent(DCB *dcb)
MXS_FREE(loopcallback);
}
spinlock_release(&dcb->cb_lock);
spinlock_acquire(&dcb->server->persistlock);
dcb->nextpersistent = dcb->server->persistent;
dcb->server->persistent = dcb;
spinlock_release(&dcb->server->persistlock);
dcb->nextpersistent = dcb->server->persistent[dcb->thread.id];
dcb->server->persistent[dcb->thread.id] = dcb;
atomic_add(&dcb->server->stats.n_persistent, 1);
atomic_add(&dcb->server->stats.n_current, -1);
return true;
@ -2580,7 +2578,7 @@ dcb_null_auth(DCB *dcb, SERVER *server, SESSION *session, GWBUF *buf)
* @return A count of the DCBs remaining in the pool
*/
int
dcb_persistent_clean_count(DCB *dcb, bool cleanall)
dcb_persistent_clean_count(DCB *dcb, int id, bool cleanall)
{
int count = 0;
if (dcb && dcb->server)
@ -2591,8 +2589,7 @@ dcb_persistent_clean_count(DCB *dcb, bool cleanall)
DCB *disposals = NULL;
CHK_SERVER(server);
spinlock_acquire(&server->persistlock);
persistentdcb = server->persistent;
persistentdcb = server->persistent[id];
while (persistentdcb)
{
CHK_DCB(persistentdcb);
@ -2611,7 +2608,7 @@ dcb_persistent_clean_count(DCB *dcb, bool cleanall)
}
else
{
server->persistent = nextdcb;
server->persistent[id] = nextdcb;
}
/* Add removed DCBs to disposal list for processing outside spinlock */
persistentdcb->nextpersistent = disposals;
@ -2626,7 +2623,7 @@ dcb_persistent_clean_count(DCB *dcb, bool cleanall)
persistentdcb = nextdcb;
}
server->persistmax = MXS_MAX(server->persistmax, count);
spinlock_release(&server->persistlock);
/** Call possible callback for this DCB in case of close */
while (disposals)
{

5
server/core/poll.c
View File

@ -445,7 +445,7 @@ poll_add_dcb(DCB *dcb)
int
poll_remove_dcb(DCB *dcb)
{
int dcbfd, rc = -1;
int dcbfd, rc = 0;
struct epoll_event ev;
CHK_DCB(dcb);
@ -493,12 +493,13 @@ poll_remove_dcb(DCB *dcb)
for (int i = 0; i < nthr; i++)
{
int tmp_rc = epoll_ctl(epoll_fd[i], EPOLL_CTL_DEL, dcb->fd, &ev);
if (tmp_rc)
if (tmp_rc && rc == 0)
{
/** Even if one of the instances failed to remove it, try
* to remove it from all the others */
rc = tmp_rc;
error_num = errno;
ss_dassert(error_num);
}
}
}

41
server/core/server.c
View File

@ -87,15 +87,18 @@ SERVER* server_alloc(const char *name, const char *address, unsigned short port,
return NULL;
}
int nthr = config_threadcount();
SERVER *server = (SERVER *)MXS_CALLOC(1, sizeof(SERVER));
char *my_name = MXS_STRDUP(name);
char *my_protocol = MXS_STRDUP(protocol);
char *my_authenticator = MXS_STRDUP(authenticator);
DCB **persistent = MXS_CALLOC(nthr, sizeof(*persistent));
if (!server || !my_name || !my_protocol || !my_authenticator)
if (!server || !my_name || !my_protocol || !my_authenticator || !persistent)
{
MXS_FREE(server);
MXS_FREE(my_name);
MXS_FREE(persistent);
MXS_FREE(my_protocol);
MXS_FREE(my_authenticator);
return NULL;
@ -125,7 +128,7 @@ SERVER* server_alloc(const char *name, const char *address, unsigned short port,
server->parameters = NULL;
server->server_string = NULL;
spinlock_init(&server->lock);
server->persistent = NULL;
server->persistent = persistent;
server->persistmax = 0;
server->persistmaxtime = 0;
server->persistpoolmax = 0;
@ -133,7 +136,6 @@ SERVER* server_alloc(const char *name, const char *address, unsigned short port,
server->monpw[0] = '\0';
server->is_active = true;
server->charset = SERVER_DEFAULT_CHARSET;
spinlock_init(&server->persistlock);
spinlock_acquire(&server_spin);
server->next = allServers;
@ -183,7 +185,12 @@ server_free(SERVER *tofreeserver)
if (tofreeserver->persistent)
{
dcb_persistent_clean_count(tofreeserver->persistent, true);
int nthr = config_threadcount();
for (int i = 0; i < nthr; i++)
{
dcb_persistent_clean_count(tofreeserver->persistent[i], i, true);
}
}
MXS_FREE(tofreeserver);
return 1;
@ -197,17 +204,16 @@ server_free(SERVER *tofreeserver)
* @param protocol The name of the protocol needed for the connection
*/
DCB *
server_get_persistent(SERVER *server, char *user, const char *protocol)
server_get_persistent(SERVER *server, char *user, const char *protocol, int id)
{
DCB *dcb, *previous = NULL;
if (server->persistent
&& dcb_persistent_clean_count(server->persistent, false)
&& server->persistent
if (server->persistent[id]
&& dcb_persistent_clean_count(server->persistent[id], id, false)
&& server->persistent[id] // Check after cleaning
&& (server->status & SERVER_RUNNING))
{
spinlock_acquire(&server->persistlock);
dcb = server->persistent;
dcb = server->persistent[id];
while (dcb)
{
if (dcb->user
@ -219,7 +225,7 @@ server_get_persistent(SERVER *server, char *user, const char *protocol)
{
if (NULL == previous)
{
server->persistent = dcb->nextpersistent;
server->persistent[id] = dcb->nextpersistent;
}
else
{
@ -227,7 +233,6 @@ server_get_persistent(SERVER *server, char *user, const char *protocol)
}
MXS_FREE(dcb->user);
dcb->user = NULL;
spinlock_release(&server->persistlock);
atomic_add(&server->stats.n_persistent, -1);
atomic_add(&server->stats.n_current, 1);
return dcb;
@ -249,7 +254,6 @@ server_get_persistent(SERVER *server, char *user, const char *protocol)
previous = dcb;
dcb = dcb->nextpersistent;
}
spinlock_release(&server->persistlock);
}
return NULL;
}
@ -549,8 +553,7 @@ dprintServer(DCB *dcb, SERVER *server)
if (server->persistpoolmax)
{
dcb_printf(dcb, "\tPersistent pool size: %d\n", server->stats.n_persistent);
dcb_printf(dcb, "\tPersistent measured pool size: %d\n",
dcb_persistent_clean_count(server->persistent, false));
dcb_printf(dcb, "\tPersistent measured pool size: %d\n", server->stats.n_persistent);
dcb_printf(dcb, "\tPersistent actual size max: %d\n", server->persistmax);
dcb_printf(dcb, "\tPersistent pool size limit: %ld\n", server->persistpoolmax);
dcb_printf(dcb, "\tPersistent max time (secs): %ld\n", server->persistmaxtime);
@ -595,19 +598,21 @@ void
dprintPersistentDCBs(DCB *pdcb, SERVER *server)
{
DCB *dcb;
int nthr = config_threadcount();
spinlock_acquire(&server->persistlock);
for (int i = 0; i < nthr; i++)
{
#if SPINLOCK_PROFILE
dcb_printf(pdcb, "DCB List Spinlock Statistics:\n");
spinlock_stats(&server->persistlock, spin_reporter, pdcb);
#endif
dcb = server->persistent;
dcb = server->persistent[i];
while (dcb)
{
dprintOneDCB(pdcb, dcb);
dcb = dcb->nextpersistent;
}
spinlock_release(&server->persistlock);
}
}
/**