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MaxScale/server/core/poll.c

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/*
* This file is distributed as part of the MariaDB Corporation MaxScale. It is free
* software: you can redistribute it and/or modify it under the terms of the
* GNU General Public License as published by the Free Software Foundation,
* version 2.
*
* This program is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
* FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
* details.
*
* You should have received a copy of the GNU General Public License along with
* this program; if not, write to the Free Software Foundation, Inc., 51
* Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Copyright MariaDB Corporation Ab 2013-2014
*/
#include <my_config.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/epoll.h>
#include <errno.h>
#include <poll.h>
#include <dcb.h>
#include <atomic.h>
#include <gwbitmask.h>
#include <skygw_utils.h>
#include <log_manager.h>
#include <gw.h>
#include <config.h>
#include <housekeeper.h>
#include <mysql.h>
#define PROFILE_POLL 1
#if PROFILE_POLL
#include <rdtsc.h>
#endif
extern int lm_enabled_logfiles_bitmask;
/**
* @file poll.c - Abstraction of the epoll functionality
*
* @verbatim
* Revision History
*
* Date Who Description
* 19/06/13 Mark Riddoch Initial implementation
* 28/06/13 Mark Riddoch Added poll mask support and DCB
* zombie management
* 29/08/14 Mark Riddoch Addition of thread status data, load average
* etc.
* 23/09/14 Mark Riddoch Make use of RDHUP conditional to allow CentOS 5
* builds.
* 24/09/14 Mark Riddoch Introduction of the event queue for processing the
* incoming events rather than processing them immediately
* in the loop after the epoll_wait. This allows for better
* thread utilisaiton and fairer scheduling of the event
* processing.
*
* @endverbatim
*/
/**
* Control the use of mutexes for the epoll_wait call. Setting to 1 will
* cause the epoll_wait calls to be moved under a mutex. This may be useful
* for debuggign purposes but should be avoided in general use.
*/
#define MUTEX_EPOLL 0
static int epoll_fd = -1; /*< The epoll file descriptor */
static int do_shutdown = 0; /*< Flag the shutdown of the poll subsystem */
static GWBITMASK poll_mask;
#if MUTEX_EPOLL
static simple_mutex_t epoll_wait_mutex; /*< serializes calls to epoll_wait */
#endif
static int n_waiting = 0; /*< No. of threads in epoll_wait */
static int process_pollq(int thread_id);
static void poll_add_event_to_dcb(DCB* dcb, GWBUF* buf, __uint32_t ev);
DCB *eventq = NULL;
SPINLOCK pollqlock = SPINLOCK_INIT;
/**
* Thread load average, this is the average number of descriptors in each
* poll completion, a value of 1 or less is the ideal.
*/
static double load_average = 0.0;
static int load_samples = 0;
static int load_nfds = 0;
static double current_avg = 0.0;
static double *avg_samples = NULL;
static int next_sample = 0;
static int n_avg_samples;
/* Thread statistics data */
static int n_threads; /*< No. of threads */
/**
* Internal MaxScale thread states
*/
typedef enum { THREAD_STOPPED, THREAD_IDLE,
THREAD_POLLING, THREAD_PROCESSING,
THREAD_ZPROCESSING } THREAD_STATE;
/**
* Thread data used to report the current state and activity related to
* a thread
*/
typedef struct {
THREAD_STATE state; /*< Current thread state */
int n_fds; /*< No. of descriptors thread is processing */
DCB *cur_dcb; /*< Current DCB being processed */
uint32_t event; /*< Current event being processed */
} THREAD_DATA;
static THREAD_DATA *thread_data = NULL; /*< Status of each thread */
/**
* The number of buckets used to gather statistics about how many
* descriptors where processed on each epoll completion.
*
* An array of wakeup counts is created, with the number of descriptors used
* to index that array. Each time a completion occurs the n_fds - 1 value is
* used to index this array and increment the count held there.
* If n_fds - 1 >= MAXFDS then the count at MAXFDS -1 is incremented.
*/
#define MAXNFDS 10
/**
* The polling statistics
*/
static struct {
int n_read; /*< Number of read events */
int n_write; /*< Number of write events */
int n_error; /*< Number of error events */
int n_hup; /*< Number of hangup events */
int n_accept; /*< Number of accept events */
int n_polls; /*< Number of poll cycles */
int n_nothreads; /*< Number of times no threads are polling */
int n_fds[MAXNFDS]; /*< Number of wakeups with particular
n_fds value */
int evq_length; /*< Event queue length */
int evq_max; /*< Maximum event queue length */
} pollStats;
/**
* How frequently to call the poll_loadav function used to monitor the load
* average of the poll subsystem.
*/
#define POLL_LOAD_FREQ 10
/**
* Periodic function to collect load data for average calculations
*/
static void poll_loadav(void *);
/**
* Initialise the polling system we are using for the gateway.
*
* In this case we are using the Linux epoll mechanism
*/
void
poll_init()
{
int i;
if (epoll_fd != -1)
return;
if ((epoll_fd = epoll_create(MAX_EVENTS)) == -1)
{
perror("epoll_create");
exit(-1);
}
memset(&pollStats, 0, sizeof(pollStats));
bitmask_init(&poll_mask);
n_threads = config_threadcount();
if ((thread_data =
(THREAD_DATA *)malloc(n_threads * sizeof(THREAD_DATA))) != NULL)
{
for (i = 0; i < n_threads; i++)
{
thread_data[i].state = THREAD_STOPPED;
}
}
#if MUTEX_EPOLL
simple_mutex_init(&epoll_wait_mutex, "epoll_wait_mutex");
#endif
hktask_add("Load Average", poll_loadav, NULL, POLL_LOAD_FREQ);
n_avg_samples = 15 * 60 / POLL_LOAD_FREQ;
avg_samples = (double *)malloc(sizeof(double *) * n_avg_samples);
for (i = 0; i < n_avg_samples; i++)
avg_samples[i] = 0.0;
}
/**
* Add a DCB to the set of descriptors within the polling
* environment.
*
* @param dcb The descriptor to add to the poll
* @return -1 on error or 0 on success
*/
int
poll_add_dcb(DCB *dcb)
{
int rc = -1;
dcb_state_t old_state = DCB_STATE_UNDEFINED;
dcb_state_t new_state;
struct epoll_event ev;
CHK_DCB(dcb);
#ifdef EPOLLRDHUP
ev.events = EPOLLIN | EPOLLOUT | EPOLLRDHUP | EPOLLHUP | EPOLLET;
#else
ev.events = EPOLLIN | EPOLLOUT | EPOLLHUP | EPOLLET;
#endif
ev.data.ptr = dcb;
/*<
* Choose new state according to the role of dcb.
*/
if (dcb->dcb_role == DCB_ROLE_REQUEST_HANDLER) {
new_state = DCB_STATE_POLLING;
} else {
ss_dassert(dcb->dcb_role == DCB_ROLE_SERVICE_LISTENER);
new_state = DCB_STATE_LISTENING;
}
/*<
* If dcb is in unexpected state, state change fails indicating that dcb
* is not polling anymore.
*/
if (dcb_set_state(dcb, new_state, &old_state)) {
rc = epoll_ctl(epoll_fd, EPOLL_CTL_ADD, dcb->fd, &ev);
if (rc != 0) {
int eno = errno;
errno = 0;
LOGIF(LE, (skygw_log_write_flush(
LOGFILE_ERROR,
"Error : Adding dcb %p in state %s "
"to poll set failed. epoll_ctl failed due "
"%d, %s.",
dcb,
STRDCBSTATE(dcb->state),
eno,
strerror(eno))));
} else {
LOGIF(LD, (skygw_log_write(
LOGFILE_DEBUG,
"%lu [poll_add_dcb] Added dcb %p in state %s to "
"poll set.",
pthread_self(),
dcb,
STRDCBSTATE(dcb->state))));
}
ss_info_dassert(rc == 0, "Unable to add poll"); /*< trap in debug */
} else {
LOGIF(LE, (skygw_log_write_flush(
LOGFILE_ERROR,
"Error : Unable to set new state for dcb %p "
"in state %s. Adding to poll set failed.",
dcb,
STRDCBSTATE(dcb->state))));
}
return rc;
}
/**
* Remove a descriptor from the set of descriptors within the
* polling environment.
* The state change command may fail because concurrent threads may call
* dcb_set_state simultaneously and the conflict is prevented in dcb_set_state.
*
* @param dcb The descriptor to remove
* @return -1 on error or 0 on success
*/
int
poll_remove_dcb(DCB *dcb)
{
struct epoll_event ev;
int rc = -1;
dcb_state_t old_state = DCB_STATE_UNDEFINED;
dcb_state_t new_state = DCB_STATE_NOPOLLING;
CHK_DCB(dcb);
/*< It is possible that dcb has already been removed from the set */
if (dcb->state != DCB_STATE_POLLING)
{
if (dcb->state == DCB_STATE_NOPOLLING ||
dcb->state == DCB_STATE_ZOMBIE)
{
rc = 0;
}
goto return_rc;
}
/*<
* Set state to NOPOLLING and remove dcb from poll set.
*/
if (dcb_set_state(dcb, new_state, &old_state)) {
rc = epoll_ctl(epoll_fd, EPOLL_CTL_DEL, dcb->fd, &ev);
if (rc != 0) {
int eno = errno;
errno = 0;
LOGIF(LE, (skygw_log_write_flush(
LOGFILE_ERROR,
"Error : epoll_ctl failed due %d, %s.",
eno,
strerror(eno))));
}
ss_dassert(rc == 0); /*< trap in debug */
}
/*<
* This call was redundant, but the end result is correct.
*/
else if (old_state == new_state)
{
rc = 0;
goto return_rc;
}
/*< Set bit for each maxscale thread */
bitmask_copy(&dcb->memdata.bitmask, poll_bitmask());
rc = 0;
return_rc:
return rc;
}
#define BLOCKINGPOLL 0 /*< Set BLOCKING POLL to 1 if using a single thread and to make
* debugging easier.
*/
/**
* The main polling loop
*
* This routine does the polling and despatches of IO events
* to the DCB's. It may be called either directly or as the entry point
* of a polling thread within the gateway.
*
* The routine will loop as long as the variable "shutdown" is set to zero,
* setting this to a non-zero value will cause the polling loop to return.
*
* There are two options for the polling, a debug option that is only useful if
* you have a single thread. This blocks in epoll_wait until an event occurs.
*
* The non-debug option does an epoll with a time out. This allows the checking of
* shutdown value to be checked in all threads. The algorithm for polling in this
* mode is to do a poll with no-wait, if no events are detected then the poll is
* repeated with a time out. This allows for a quick check before making the call
* with timeout. The call with the timeout differs in that the Linux scheduler may
* deschedule a process if a timeout is included, but will not do this if a 0 timeout
* value is given. this improves performance when the gateway is under heavy load.
*
* In order to provide a fairer means of sharign the threads between the different
* DCB's the poll mechanism has been decoupled from the processing of the events.
* The events are now recieved via the epoll_wait call, a queue of DCB's that have
* events pending is maintained and as new events arrive the DCB is added to the end
* of this queue. If an eent arrives for a DCB alreayd in the queue, then the event
* bits are added to the DCB but the DCB mantains the same point in the queue unless
* the original events are already being processed. If they are being processed then
* the DCB is moved to the back of the queue, this means that a DCB that is receiving
* events at a high rate will not block the execution of events for other DCB's and
* should result in a fairer polling strategy.
*
* @param arg The thread ID passed as a void * to satisfy the threading package
*/
void
poll_waitevents(void *arg)
{
struct epoll_event events[MAX_EVENTS];
int i, nfds;
int thread_id = (int)arg;
DCB *zombies = NULL;
/** Add this thread to the bitmask of running polling threads */
bitmask_set(&poll_mask, thread_id);
if (thread_data)
{
thread_data[thread_id].state = THREAD_IDLE;
}
/** Init mysql thread context for use with a mysql handle and a parser */
mysql_thread_init();
while (1)
{
/* Process of the queue of waiting requests */
while (do_shutdown == 0 && process_pollq(thread_id))
{
if (thread_data)
thread_data[thread_id].state = THREAD_ZPROCESSING;
zombies = dcb_process_zombies(thread_id);
}
atomic_add(&n_waiting, 1);
#if BLOCKINGPOLL
nfds = epoll_wait(epoll_fd, events, MAX_EVENTS, -1);
atomic_add(&n_waiting, -1);
#else /* BLOCKINGPOLL */
#if MUTEX_EPOLL
simple_mutex_lock(&epoll_wait_mutex, TRUE);
#endif
if (thread_data)
{
thread_data[thread_id].state = THREAD_POLLING;
}
if ((nfds = epoll_wait(epoll_fd, events, MAX_EVENTS, 0)) == -1)
{
atomic_add(&n_waiting, -1);
int eno = errno;
errno = 0;
LOGIF(LD, (skygw_log_write(
LOGFILE_DEBUG,
"%lu [poll_waitevents] epoll_wait returned "
"%d, errno %d",
pthread_self(),
nfds,
eno)));
}
/*
* If there are no new descriptors from the non-blocking call
* and nothing to proces on the event queue then for do a
* blocking call to epoll_wait.
*/
else if (nfds == 0 && process_pollq(thread_id) == 0)
{
atomic_add(&n_waiting, 1);
nfds = epoll_wait(epoll_fd,
events,
MAX_EVENTS,
EPOLL_TIMEOUT);
}
else
{
atomic_add(&n_waiting, -1);
}
if (n_waiting == 0)
atomic_add(&pollStats.n_nothreads, 1);
#if MUTEX_EPOLL
simple_mutex_unlock(&epoll_wait_mutex);
#endif
#endif /* BLOCKINGPOLL */
if (nfds > 0)
{
LOGIF(LD, (skygw_log_write(
LOGFILE_DEBUG,
"%lu [poll_waitevents] epoll_wait found %d fds",
pthread_self(),
nfds)));
atomic_add(&pollStats.n_polls, 1);
if (thread_data)
{
thread_data[thread_id].n_fds = nfds;
thread_data[thread_id].cur_dcb = NULL;
thread_data[thread_id].event = 0;
thread_data[thread_id].state = THREAD_PROCESSING;
}
pollStats.n_fds[(nfds < MAXNFDS ? (nfds - 1) : MAXNFDS - 1)]++;
load_average = (load_average * load_samples + nfds)
/ (load_samples + 1);
atomic_add(&load_samples, 1);
atomic_add(&load_nfds, nfds);
/*
* Process every DCB that has a new event and add
* it to the poll queue.
* If the DCB is currently beign processed then we
* or in the new eent bits to the pending event bits
* and leave it in the queue.
* If the DCB was not already in the queue then it was
* idle and is added to the queue to process after
* setting the event bits.
*/
for (i = 0; i < nfds; i++)
{
DCB *dcb = (DCB *)events[i].data.ptr;
__uint32_t ev = events[i].events;
spinlock_acquire(&pollqlock);
if (DCB_POLL_BUSY(dcb))
{
dcb->evq.pending_events |= ev;
}
else
{
dcb->evq.pending_events = ev;
if (eventq)
{
dcb->evq.prev = eventq->evq.prev;
eventq->evq.prev->evq.next = dcb;
eventq->evq.prev = dcb;
dcb->evq.next = eventq;
}
else
{
eventq = dcb;
dcb->evq.prev = dcb;
dcb->evq.next = dcb;
}
pollStats.evq_length++;
if (pollStats.evq_length > pollStats.evq_max)
{
pollStats.evq_max = pollStats.evq_length;
}
}
spinlock_release(&pollqlock);
}
}
/*
* If there was nothing to process then process the zombie queue
*/
if (process_pollq(thread_id) == 0)
{
if (thread_data)
{
thread_data[thread_id].state = THREAD_ZPROCESSING;
}
zombies = dcb_process_zombies(thread_id);
}
if (do_shutdown)
{
/*<
* Remove the thread from the bitmask of running
* polling threads.
*/
if (thread_data)
{
thread_data[thread_id].state = THREAD_STOPPED;
}
bitmask_clear(&poll_mask, thread_id);
/** Release mysql thread context */
mysql_thread_end();
return;
}
if (thread_data)
{
thread_data[thread_id].state = THREAD_IDLE;
}
} /*< while(1) */
}
/**
* Process of the queue of DCB's that have outstanding events
*
* The first event on the queue will be chosen to be executed by this thread,
* all other events will be left on the queue and may be picked up by other
* threads. When the processing is complete the thread will take the DCB off the
* queue if there are no pending events that have arrived since the thread started
* to process the DCB. If there are pending events the DCB will be moved to the
* back of the queue so that other DCB's will have a share of the threads to
* execute events for them.
*
* @param thread_id The thread ID of the calling thread
* @return 0 if no DCB's have been processed
*/
static int
process_pollq(int thread_id)
{
DCB *dcb;
int found = 0;
uint32_t ev;
spinlock_acquire(&pollqlock);
if (eventq == NULL)
{
/* Nothing to process */
spinlock_release(&pollqlock);
return 0;
}
dcb = eventq;
if (dcb->evq.next == dcb->evq.prev && dcb->evq.processing == 0)
{
found = 1;
dcb->evq.processing = 1;
}
else if (dcb->evq.next == dcb->evq.prev)
{
/* Only item in queue is being processed */
spinlock_release(&pollqlock);
return 0;
}
else
{
do {
dcb = dcb->evq.next;
} while (dcb != eventq && dcb->evq.processing == 1);
if (dcb->evq.processing == 0)
{
/* Found DCB to process */
dcb->evq.processing = 1;
found = 1;
}
}
if (found)
{
ev = dcb->evq.pending_events;
dcb->evq.pending_events = 0;
}
spinlock_release(&pollqlock);
if (found == 0)
return 0;
CHK_DCB(dcb);
if (thread_data)
{
thread_data[thread_id].state = THREAD_PROCESSING;
thread_data[thread_id].cur_dcb = dcb;
thread_data[thread_id].event = ev;
}
#if defined(FAKE_CODE)
if (dcb_fake_write_ev[dcb->fd] != 0) {
LOGIF(LD, (skygw_log_write(
LOGFILE_DEBUG,
"%lu [poll_waitevents] "
"Added fake events %d to ev %d.",
pthread_self(),
dcb_fake_write_ev[dcb->fd],
ev)));
ev |= dcb_fake_write_ev[dcb->fd];
dcb_fake_write_ev[dcb->fd] = 0;
}
#endif /* FAKE_CODE */
ss_debug(spinlock_acquire(&dcb->dcb_initlock);)
ss_dassert(dcb->state != DCB_STATE_ALLOC);
ss_dassert(dcb->state != DCB_STATE_DISCONNECTED);
ss_dassert(dcb->state != DCB_STATE_FREED);
ss_debug(spinlock_release(&dcb->dcb_initlock);)
LOGIF(LD, (skygw_log_write(
LOGFILE_DEBUG,
"%lu [poll_waitevents] event %d dcb %p "
"role %s",
pthread_self(),
ev,
dcb,
STRDCBROLE(dcb->dcb_role))));
if (ev & EPOLLOUT)
{
int eno = 0;
eno = gw_getsockerrno(dcb->fd);
if (eno == 0) {
#if MUTEX_BLOCK
simple_mutex_lock(
&dcb->dcb_write_lock,
true);
ss_info_dassert(
!dcb->dcb_write_active,
"Write already active");
dcb->dcb_write_active = TRUE;
atomic_add(
&pollStats.n_write,
1);
dcb->func.write_ready(dcb);
dcb->dcb_write_active = FALSE;
simple_mutex_unlock(
&dcb->dcb_write_lock);
#else
atomic_add(&pollStats.n_write,
1);
dcb->func.write_ready(dcb);
#endif
} else {
LOGIF(LD, (skygw_log_write(
LOGFILE_DEBUG,
"%lu [poll_waitevents] "
"EPOLLOUT due %d, %s. "
"dcb %p, fd %i",
pthread_self(),
eno,
strerror(eno),
dcb,
dcb->fd)));
}
}
if (ev & EPOLLIN)
{
#if MUTEX_BLOCK
simple_mutex_lock(&dcb->dcb_read_lock,
true);
ss_info_dassert(!dcb->dcb_read_active,
"Read already active");
dcb->dcb_read_active = TRUE;
#endif
if (dcb->state == DCB_STATE_LISTENING)
{
LOGIF(LD, (skygw_log_write(
LOGFILE_DEBUG,
"%lu [poll_waitevents] "
"Accept in fd %d",
pthread_self(),
dcb->fd)));
atomic_add(
&pollStats.n_accept, 1);
dcb->func.accept(dcb);
}
else
{
LOGIF(LD, (skygw_log_write(
LOGFILE_DEBUG,
"%lu [poll_waitevents] "
"Read in dcb %p fd %d",
pthread_self(),
dcb,
dcb->fd)));
atomic_add(&pollStats.n_read, 1);
dcb->func.read(dcb);
}
#if MUTEX_BLOCK
dcb->dcb_read_active = FALSE;
simple_mutex_unlock(
&dcb->dcb_read_lock);
#endif
}
if (ev & EPOLLERR)
{
int eno = gw_getsockerrno(dcb->fd);
#if defined(FAKE_CODE)
if (eno == 0) {
eno = dcb_fake_write_errno[dcb->fd];
LOGIF(LD, (skygw_log_write(
LOGFILE_DEBUG,
"%lu [poll_waitevents] "
"Added fake errno %d. "
"%s",
pthread_self(),
eno,
strerror(eno))));
}
dcb_fake_write_errno[dcb->fd] = 0;
#endif /* FAKE_CODE */
if (eno != 0) {
LOGIF(LD, (skygw_log_write(
LOGFILE_DEBUG,
"%lu [poll_waitevents] "
"EPOLLERR due %d, %s.",
pthread_self(),
eno,
strerror(eno))));
}
atomic_add(&pollStats.n_error, 1);
dcb->func.error(dcb);
}
if (ev & EPOLLHUP)
{
int eno = 0;
eno = gw_getsockerrno(dcb->fd);
LOGIF(LD, (skygw_log_write(
LOGFILE_DEBUG,
"%lu [poll_waitevents] "
"EPOLLHUP on dcb %p, fd %d. "
"Errno %d, %s.",
pthread_self(),
dcb,
dcb->fd,
eno,
strerror(eno))));
atomic_add(&pollStats.n_hup, 1);
spinlock_acquire(&dcb->dcb_initlock);
if ((dcb->flags & DCBF_HUNG) == 0)
{
dcb->flags |= DCBF_HUNG;
spinlock_release(&dcb->dcb_initlock);
dcb->func.hangup(dcb);
}
else
spinlock_release(&dcb->dcb_initlock);
}
#ifdef EPOLLRDHUP
if (ev & EPOLLRDHUP)
{
int eno = 0;
eno = gw_getsockerrno(dcb->fd);
LOGIF(LD, (skygw_log_write(
LOGFILE_DEBUG,
"%lu [poll_waitevents] "
"EPOLLRDHUP on dcb %p, fd %d. "
"Errno %d, %s.",
pthread_self(),
dcb,
dcb->fd,
eno,
strerror(eno))));
atomic_add(&pollStats.n_hup, 1);
spinlock_acquire(&dcb->dcb_initlock);
if ((dcb->flags & DCBF_HUNG) == 0)
{
dcb->flags |= DCBF_HUNG;
spinlock_release(&dcb->dcb_initlock);
dcb->func.hangup(dcb);
}
else
spinlock_release(&dcb->dcb_initlock);
}
#endif
spinlock_acquire(&pollqlock);
if (dcb->evq.pending_events == 0)
{
/* No pending events so remove from the queue */
if (dcb->evq.prev != dcb)
{
dcb->evq.prev->evq.next = dcb->evq.next;
dcb->evq.next->evq.prev = dcb->evq.prev;
if (eventq == dcb)
eventq = dcb->evq.next;
}
else
{
eventq = NULL;
}
dcb->evq.next = NULL;
dcb->evq.prev = NULL;
pollStats.evq_length--;
}
else
{
/*
* We have a pending event, move to the end of the queue
* if there are any other DCB's in the queue.
*
* If we are the first item on the queue this is easy, we
* just bump the eventq pointer.
*/
if (dcb->evq.prev != dcb)
{
if (eventq == dcb)
eventq = dcb->evq.next;
else
{
dcb->evq.prev->evq.next = dcb->evq.next;
dcb->evq.next->evq.prev = dcb->evq.prev;
dcb->evq.prev = eventq->evq.prev;
dcb->evq.next = eventq;
eventq->evq.prev = dcb;
dcb->evq.prev->evq.next = dcb;
}
}
}
dcb->evq.processing = 0;
spinlock_release(&pollqlock);
return 1;
}
/**
* Shutdown the polling loop
*/
void
poll_shutdown()
{
do_shutdown = 1;
}
/**
* Return the bitmask of polling threads
*
* @return The bitmask of the running polling threads
*/
GWBITMASK *
poll_bitmask()
{
return &poll_mask;
}
/**
* Display an entry from the spinlock statistics data
*
* @param dcb The DCB to print to
* @param desc Description of the statistic
* @param value The statistic value
*/
static void
spin_reporter(void *dcb, char *desc, int value)
{
dcb_printf((DCB *)dcb, "\t%-40s %d\n", desc, value);
}
/**
* Debug routine to print the polling statistics
*
* @param dcb DCB to print to
*/
void
dprintPollStats(DCB *dcb)
{
int i;
dcb_printf(dcb, "Number of epoll cycles: %d\n",
pollStats.n_polls);
dcb_printf(dcb, "Number of read events: %d\n",
pollStats.n_read);
dcb_printf(dcb, "Number of write events: %d\n",
pollStats.n_write);
dcb_printf(dcb, "Number of error events: %d\n",
pollStats.n_error);
dcb_printf(dcb, "Number of hangup events: %d\n",
pollStats.n_hup);
dcb_printf(dcb, "Number of accept events: %d\n",
pollStats.n_accept);
dcb_printf(dcb, "Number of times no threads polling: %d\n",
pollStats.n_nothreads);
dcb_printf(dcb, "Current event queue length: %d\n",
pollStats.evq_length);
dcb_printf(dcb, "Maximum event queue length: %d\n",
pollStats.evq_max);
dcb_printf(dcb, "No of poll completions with descriptors\n");
dcb_printf(dcb, "\tNo. of descriptors\tNo. of poll completions.\n");
for (i = 0; i < MAXNFDS - 1; i++)
{
dcb_printf(dcb, "\t%2d\t\t\t%d\n", i + 1, pollStats.n_fds[i]);
}
dcb_printf(dcb, "\t>= %d\t\t\t%d\n", MAXNFDS,
pollStats.n_fds[MAXNFDS-1]);
#if SPINLOCK_PROFILE
dcb_printf(dcb, "Event queue lock statistics:\n");
spinlock_stats(&pollqlock, spin_reporter, dcb);
#endif
}
/**
* Convert an EPOLL event mask into a printable string
*
* @param event The event mask
* @return A string representation, the caller must free the string
*/
static char *
event_to_string(uint32_t event)
{
char *str;
str = malloc(22); // 22 is max returned string length
if (str == NULL)
return NULL;
*str = 0;
if (event & EPOLLIN)
{
strcat(str, "IN");
}
if (event & EPOLLOUT)
{
if (*str)
strcat(str, "|");
strcat(str, "OUT");
}
if (event & EPOLLERR)
{
if (*str)
strcat(str, "|");
strcat(str, "ERR");
}
if (event & EPOLLHUP)
{
if (*str)
strcat(str, "|");
strcat(str, "HUP");
}
#ifdef EPOLLRDHUP
if (event & EPOLLRDHUP)
{
if (*str)
strcat(str, "|");
strcat(str, "RDHUP");
}
#endif
return str;
}
/**
* Print the thread status for all the polling threads
*
* @param dcb The DCB to send the thread status data
*/
void
dShowThreads(DCB *dcb)
{
int i, j, n;
char *state;
double avg1 = 0.0, avg5 = 0.0, avg15 = 0.0;
dcb_printf(dcb, "Polling Threads.\n\n");
dcb_printf(dcb, "Historic Thread Load Average: %.2f.\n", load_average);
dcb_printf(dcb, "Current Thread Load Average: %.2f.\n", current_avg);
/* Average all the samples to get the 15 minute average */
for (i = 0; i < n_avg_samples; i++)
avg15 += avg_samples[i];
avg15 = avg15 / n_avg_samples;
/* Average the last third of the samples to get the 5 minute average */
n = 5 * 60 / POLL_LOAD_FREQ;
i = next_sample - (n + 1);
if (i < 0)
i += n_avg_samples;
for (j = i; j < i + n; j++)
avg5 += avg_samples[j % n_avg_samples];
avg5 = (3 * avg5) / (n_avg_samples);
/* Average the last 15th of the samples to get the 1 minute average */
n = 60 / POLL_LOAD_FREQ;
i = next_sample - (n + 1);
if (i < 0)
i += n_avg_samples;
for (j = i; j < i + n; j++)
avg1 += avg_samples[j % n_avg_samples];
avg1 = (15 * avg1) / (n_avg_samples);
dcb_printf(dcb, "15 Minute Average: %.2f, 5 Minute Average: %.2f, "
"1 Minute Average: %.2f\n\n", avg15, avg5, avg1);
if (thread_data == NULL)
return;
dcb_printf(dcb, " ID | State | # fds | Descriptor | Event\n");
dcb_printf(dcb, "----+------------+--------+------------------+---------------\n");
for (i = 0; i < n_threads; i++)
{
switch (thread_data[i].state)
{
case THREAD_STOPPED:
state = "Stopped";
break;
case THREAD_IDLE:
state = "Idle";
break;
case THREAD_POLLING:
state = "Polling";
break;
case THREAD_PROCESSING:
state = "Processing";
break;
case THREAD_ZPROCESSING:
state = "Collecting";
break;
}
if (thread_data[i].state != THREAD_PROCESSING)
dcb_printf(dcb,
" %2d | %-10s | | |\n",
i, state);
else if (thread_data[i].cur_dcb == NULL)
dcb_printf(dcb,
" %2d | %-10s | %6d | |\n",
i, state, thread_data[i].n_fds);
else
{
char *event_string
= event_to_string(thread_data[i].event);
bool from_heap;
if (event_string == NULL)
{
from_heap = false;
event_string = "??";
}
else
{
from_heap = true;
}
dcb_printf(dcb,
" %2d | %-10s | %6d | %-16p | %s\n",
i, state, thread_data[i].n_fds,
thread_data[i].cur_dcb, event_string);
if (from_heap)
{
free(event_string);
}
}
}
}
/**
* The function used to calculate time based load data. This is called by the
* housekeeper every POLL_LOAD_FREQ seconds.
*
* @param data Argument required by the housekeeper but not used here
*/
static void
poll_loadav(void *data)
{
static int last_samples = 0, last_nfds = 0;
int new_samples, new_nfds;
new_samples = load_samples - last_samples;
new_nfds = load_nfds - last_nfds;
last_samples = load_samples;
last_nfds = load_nfds;
/* POLL_LOAD_FREQ average is... */
if (new_samples)
current_avg = new_nfds / new_samples;
else
current_avg = 0.0;
avg_samples[next_sample] = current_avg;
next_sample++;
if (next_sample >= n_avg_samples)
next_sample = 0;
}
/**
* Add given GWBUF to DCB's readqueue and add a pending EPOLLIN event for DCB.
* The event pretends that there is something to read for the DCB. Actually
* the incoming data is stored in the DCB's readqueue where it is read.
*
* @param dcb DCB where the event and data are added
* @param buf GWBUF including the data
*
*/
void poll_add_epollin_event_to_dcb(
DCB* dcb,
GWBUF* buf)
{
__uint32_t ev;
ev = EPOLLIN;
poll_add_event_to_dcb(dcb, buf, ev);
}
static void poll_add_event_to_dcb(
DCB* dcb,
GWBUF* buf,
__uint32_t ev)
{
/** Add buf to readqueue */
spinlock_acquire(&dcb->authlock);
dcb->dcb_readqueue = gwbuf_append(dcb->dcb_readqueue, buf);
spinlock_release(&dcb->authlock);
spinlock_acquire(&pollqlock);
/** Set event to DCB */
if (DCB_POLL_BUSY(dcb))
{
dcb->evq.pending_events |= ev;
}
else
{
dcb->evq.pending_events = ev;
/** Add DCB to eventqueue if it isn't already there */
if (eventq)
{
dcb->evq.prev = eventq->evq.prev;
eventq->evq.prev->evq.next = dcb;
eventq->evq.prev = dcb;
dcb->evq.next = eventq;
}
else
{
eventq = dcb;
dcb->evq.prev = dcb;
dcb->evq.next = dcb;
}
pollStats.evq_length++;
if (pollStats.evq_length > pollStats.evq_max)
{
pollStats.evq_max = pollStats.evq_length;
}
}
spinlock_release(&pollqlock);
}
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