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/*
  Copyright (c) 2006-2009 Z RESEARCH, Inc. <http://www.zresearch.com>
  This file is part of GlusterFS.

  GlusterFS 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; either version 3 of the License,
  or (at your option) any later version.

  GlusterFS 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, see
  <http://www.gnu.org/licenses/>.
*/

#ifndef __IOT_H
#define __IOT_H

#ifndef _CONFIG_H
#define _CONFIG_H
#include "config.h"
#endif


#include "compat-errno.h"
#include "glusterfs.h"
#include "logging.h"
#include "dict.h"
#include "xlator.h"
#include "common-utils.h"
#include "list.h"
#include <stdlib.h>

#define min(a,b) ((a)<(b)?(a):(b))
#define max(a,b) ((a)>(b)?(a):(b))

struct iot_conf;
struct iot_worker;
struct iot_request;

struct iot_request {
        struct list_head list;        /* Attaches this request to the list of
                                         requests.
                                      */
        call_stub_t *stub;
};

typedef enum {
        IOT_STATE_ACTIVE,
        IOT_STATE_EXIT_REQUEST,
        IOT_STATE_DEAD
}iot_state_t;
#define iot_worker_active(wrk)  ((wrk)->state == IOT_STATE_ACTIVE)

#define MAX_IDLE_SKEW                   1000    /* usecs */
#define skew_usec_idle_time(usec)       ((usec) + (random () % MAX_IDLE_SKEW))
#define IOT_DEFAULT_IDLE                180     /* In secs. */

#define IOT_MIN_THREADS         2
#define IOT_DEFAULT_THREADS     16
#define IOT_MAX_THREADS         256

#define IOT_SCALING_OFF                 _gf_false
#define IOT_SCALING_ON                  _gf_true
#define iot_ordered_scaling_on(conf)    ((conf)->o_scaling == IOT_SCALING_ON)
#define iot_unordered_scaling_on(conf)  ((conf)->u_scaling == IOT_SCALING_ON)

#define IOT_THREAD_STACK_SIZE   ((size_t)(1024*1024))

/* This signifies the max number of outstanding request we're expecting
 * at a point for every worker thread.
 * For an idea of the memory foot-print, consider at most 16 Bytes per
 * iot_request_t on a 64-bit system with another 16 bytes per chunk in the
 * header. For 64 slots in the pool, we'll use up 2 KiB, with 64 threads this
 * goes up to 128 KiB.
 *
 * Note that this size defines the size of the per-worker mem pool. The
 * advantage is that, we're not only reducing the rate of small iot_request_t
 * allocations from the heap but also reducing the contention on the libc heap
 * by having a mem pool, though small, for each worker.
 */
#define IOT_REQUEST_MEMPOOL_SIZE        64

struct iot_worker {
        struct list_head rqlist;      /* List of requests assigned to me. */
        struct iot_conf  *conf;
        int64_t          q,dq;
        pthread_cond_t   dq_cond;
        pthread_mutex_t  qlock;
        int32_t          queue_size;
        pthread_t        thread;
        iot_state_t      state;            /* What state is the thread in. */
        int              thread_idx;       /* Thread's index into the worker
                                              array. Since this will be thread
                                              local data, for ensuring that
                                              number of threads dont fall below
                                              a minimum, we just dont allow
                                              threads with specific indices to
                                              exit. Helps us in eliminating one
                                              place where otherwise a lock
                                              would have been required to update
                                              centralized state inside conf.
                                           */
        struct mem_pool  *req_pool;    /* iot_request_t's come from here. */
};

struct iot_conf {
        int32_t              thread_count;
        struct iot_worker  **workers;

        xlator_t            *this;
        /* Config state for ordered threads. */
        pthread_mutex_t      otlock;       /* Used to sync any state that needs
                                              to be changed by the ordered
                                              threads.
                                           */

        int                  max_o_threads; /* Max. number of ordered threads */
        int                  min_o_threads; /* Min. number of ordered threads.
                                               Ordered thread count never falls
                                               below this threshold.
                                            */

        int                  o_idle_time;   /* in Secs. The idle time after
                                               which an ordered thread exits.
                                            */
        gf_boolean_t         o_scaling;     /* Set to IOT_SCALING_OFF if user
                                               does not want thread scaling on
                                               ordered threads. If scaling is
                                               off, io-threads maintains at
                                               least min_o_threads number of
                                               threads and never lets any thread
                                               exit.
                                            */
        struct iot_worker  **oworkers;      /* Ordered thread pool. */


        /* Config state for unordered threads */
        pthread_mutex_t      utlock;       /* Used for scaling un-ordered
                                              threads. */
        struct iot_worker  **uworkers;     /* Un-ordered thread pool. */
        int                  max_u_threads; /* Number of unordered threads will
                                               not be higher than this. */
        int                  min_u_threads; /* Number of unordered threads
                                               should not fall below this value.
                                            */
        int                  u_idle_time;   /* If an unordered thread does not
                                               get a request for this amount of
                                               secs, it should try to die.
                                            */
        gf_boolean_t         u_scaling;     /* Set to IOT_SCALING_OFF if user
                                               does not want thread scaling on
                                               unordered threads. If scaling is
                                               off, io-threads maintains at
                                               least min_u_threads number of
                                               threads and never lets any thread
                                               exit.
                                            */

        pthread_attr_t       w_attr;        /* Used to reduce the stack size of
                                               the pthread worker down from the
                                               default of 8MiB.
                                            */
};

typedef struct iot_conf iot_conf_t;
typedef struct iot_worker iot_worker_t;
typedef struct iot_request iot_request_t;

#endif /* __IOT_H */