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mirror_zfs/include/sys/tsd.h

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Add Thread Specific Data (TSD) Implementation Thread specific data has implemented using a hash table, this avoids the need to add a member to the task structure and allows maximum portability between kernels. This implementation has been optimized to keep the tsd_set() and tsd_get() times as small as possible. The majority of the entries in the hash table are for specific tsd entries. These entries are hashed by the product of their key and pid because by design the key and pid are guaranteed to be unique. Their product also has the desirable properly that it will be uniformly distributed over the hash bins providing neither the pid nor key is zero. Under linux the zero pid is always the init process and thus won't be used, and this implementation is careful to never to assign a zero key. By default the hash table is sized to 512 bins which is expected to be sufficient for light to moderate usage of thread specific data. The hash table contains two additional type of entries. They first type is entry is called a 'key' entry and it is added to the hash during tsd_create(). It is used to store the address of the destructor function and it is used as an anchor point. All tsd entries which use the same key will be linked to this entry. This is used during tsd_destory() to quickly call the destructor function for all tsd associated with the key. The 'key' entry may be looked up with tsd_hash_search() by passing the key you wish to lookup and DTOR_PID constant as the pid. The second type of entry is called a 'pid' entry and it is added to the hash the first time a process set a key. The 'pid' entry is also used as an anchor and all tsd for the process will be linked to it. This list is using during tsd_exit() to ensure all registered destructors are run for the process. The 'pid' entry may be looked up with tsd_hash_search() by passing the PID_KEY constant as the key, and the process pid. Note that tsd_exit() is called by thread_exit() so if your using the Solaris thread API you should not need to call tsd_exit() directly.
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/*****************************************************************************\
* Copyright (C) 2010 Lawrence Livermore National Security, LLC.
* Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER).
* Written by Brian Behlendorf <behlendorf1@llnl.gov>.
* UCRL-CODE-235197
*
* This file is part of the SPL, Solaris Porting Layer.
Refresh links to web site Update links to refer to the official ZFS on Linux website instead of @behlendorf's personal fork on github. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2013-03-05 05:26:55 +04:00
* For details, see <http://zfsonlinux.org/>.
Add Thread Specific Data (TSD) Implementation Thread specific data has implemented using a hash table, this avoids the need to add a member to the task structure and allows maximum portability between kernels. This implementation has been optimized to keep the tsd_set() and tsd_get() times as small as possible. The majority of the entries in the hash table are for specific tsd entries. These entries are hashed by the product of their key and pid because by design the key and pid are guaranteed to be unique. Their product also has the desirable properly that it will be uniformly distributed over the hash bins providing neither the pid nor key is zero. Under linux the zero pid is always the init process and thus won't be used, and this implementation is careful to never to assign a zero key. By default the hash table is sized to 512 bins which is expected to be sufficient for light to moderate usage of thread specific data. The hash table contains two additional type of entries. They first type is entry is called a 'key' entry and it is added to the hash during tsd_create(). It is used to store the address of the destructor function and it is used as an anchor point. All tsd entries which use the same key will be linked to this entry. This is used during tsd_destory() to quickly call the destructor function for all tsd associated with the key. The 'key' entry may be looked up with tsd_hash_search() by passing the key you wish to lookup and DTOR_PID constant as the pid. The second type of entry is called a 'pid' entry and it is added to the hash the first time a process set a key. The 'pid' entry is also used as an anchor and all tsd for the process will be linked to it. This list is using during tsd_exit() to ensure all registered destructors are run for the process. The 'pid' entry may be looked up with tsd_hash_search() by passing the PID_KEY constant as the key, and the process pid. Note that tsd_exit() is called by thread_exit() so if your using the Solaris thread API you should not need to call tsd_exit() directly.
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*
* The SPL 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 2 of the License, or (at your
* option) any later version.
*
* The SPL 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 the SPL. If not, see <http://www.gnu.org/licenses/>.
\*****************************************************************************/
#ifndef _SPL_TSD_H
#define _SPL_TSD_H
#include <sys/types.h>
#define TSD_HASH_TABLE_BITS_DEFAULT 9
#define TSD_KEYS_MAX 32768
#define DTOR_PID (PID_MAX_LIMIT+1)
#define PID_KEY (TSD_KEYS_MAX+1)
typedef void (*dtor_func_t)(void *);
extern int tsd_set(uint_t, void *);
extern void *tsd_get(uint_t);
extern void tsd_create(uint_t *, dtor_func_t);
extern void tsd_destroy(uint_t *);
extern void tsd_exit(void);
Prepend spl_ to all init/fini functions This is a bit of cleanup I'd been meaning to get to for a while to reduce the chance of a type conflict. Well that conflict finally occurred with the kstat_init() function which conflicts with a function in the 2.6.32-6-pve kernel. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #56
2011-11-11 21:03:31 +04:00
int spl_tsd_init(void);
void spl_tsd_fini(void);
Add Thread Specific Data (TSD) Implementation Thread specific data has implemented using a hash table, this avoids the need to add a member to the task structure and allows maximum portability between kernels. This implementation has been optimized to keep the tsd_set() and tsd_get() times as small as possible. The majority of the entries in the hash table are for specific tsd entries. These entries are hashed by the product of their key and pid because by design the key and pid are guaranteed to be unique. Their product also has the desirable properly that it will be uniformly distributed over the hash bins providing neither the pid nor key is zero. Under linux the zero pid is always the init process and thus won't be used, and this implementation is careful to never to assign a zero key. By default the hash table is sized to 512 bins which is expected to be sufficient for light to moderate usage of thread specific data. The hash table contains two additional type of entries. They first type is entry is called a 'key' entry and it is added to the hash during tsd_create(). It is used to store the address of the destructor function and it is used as an anchor point. All tsd entries which use the same key will be linked to this entry. This is used during tsd_destory() to quickly call the destructor function for all tsd associated with the key. The 'key' entry may be looked up with tsd_hash_search() by passing the key you wish to lookup and DTOR_PID constant as the pid. The second type of entry is called a 'pid' entry and it is added to the hash the first time a process set a key. The 'pid' entry is also used as an anchor and all tsd for the process will be linked to it. This list is using during tsd_exit() to ensure all registered destructors are run for the process. The 'pid' entry may be looked up with tsd_hash_search() by passing the PID_KEY constant as the key, and the process pid. Note that tsd_exit() is called by thread_exit() so if your using the Solaris thread API you should not need to call tsd_exit() directly.
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#endif /* _SPL_TSD_H */
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