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| author | Lorry Tar Creator <lorry-tar-importer@baserock.org> | 2015-02-17 17:25:57 +0000 |
|---|---|---|
| committer | <> | 2015-03-17 16:26:24 +0000 |
| commit | 780b92ada9afcf1d58085a83a0b9e6bc982203d1 (patch) | |
| tree | 598f8b9fa431b228d29897e798de4ac0c1d3d970 /docs/programmer_reference/env_size.html | |
| parent | 7a2660ba9cc2dc03a69ddfcfd95369395cc87444 (diff) | |
| download | berkeleydb-master.tar.gz | |
Diffstat (limited to 'docs/programmer_reference/env_size.html')
| -rw-r--r-- | docs/programmer_reference/env_size.html | 139 |
1 files changed, 72 insertions, 67 deletions
diff --git a/docs/programmer_reference/env_size.html b/docs/programmer_reference/env_size.html index 78f1398d..de849860 100644 --- a/docs/programmer_reference/env_size.html +++ b/docs/programmer_reference/env_size.html @@ -14,7 +14,7 @@ <body> <div xmlns="" class="navheader"> <div class="libver"> - <p>Library Version 11.2.5.3</p> + <p>Library Version 12.1.6.1</p> </div> <table width="100%" summary="Navigation header"> <tr> @@ -22,9 +22,7 @@ </tr> <tr> <td width="20%" align="left"><a accesskey="p" href="env_create.html">Prev</a> </td> - <th width="60%" align="center">Chapter 9. - The Berkeley DB Environment - </th> + <th width="60%" align="center">Chapter 9. The Berkeley DB Environment </th> <td width="20%" align="right"> <a accesskey="n" href="env_open.html">Next</a></td> </tr> </table> @@ -40,15 +38,16 @@ </div> <p> The Berkeley DB environment allocates memory to hold shared - structures, either in shared regions or in process data space (if the - <a href="../api_reference/C/envopen.html#envopen_DB_PRIVATE" class="olink">DB_PRIVATE</a> flag is specified). There are three distinct memory - regions: + structures, either in shared regions or in process data space + (if the <a href="../api_reference/C/envopen.html#envopen_DB_PRIVATE" class="olink">DB_PRIVATE</a> flag is specified). There are three + distinct memory regions: </p> <div class="itemizedlist"> <ul type="disc"> <li> <p> - The memory pool (also known as the database page cache), + The memory pool (also known as the database page + cache), </p> </li> <li> @@ -57,32 +56,32 @@ </p> </li> <li> - <p> - the main region which holds all other shared structures. + <p> + the main region which holds all other shared + structures. </p> </li> </ul> </div> <p> - The shared structures in the main region are used by the lock, - transaction, logging, thread and replicatoin subsystems. + The shared structures in the main region are used by the + lock, transaction, logging, thread and replicatoin subsystems. </p> <p> - Determining the amount of space allocated for each of these shared - structures is dependent upon the structure in question. The sizing - of the memory pool is discussed in - <a class="xref" href="mp_config.html" title="Configuring the memory pool">Configuring the memory pool</a>. The amount - of memory needed for mutexes is calculated from the number of - mutexes needed by various subsystems and can be adjusted using the - <a href="../api_reference/C/mutexset_increment.html" class="olink">DB_ENV->mutex_set_increment()</a> method. + Determining the amount of space allocated for each of these + shared structures is dependent upon the structure in question. + The sizing of the memory pool is discussed in <a class="xref" href="mp_config.html" title="Configuring the memory pool">Configuring the memory pool</a>. The + amount of memory needed for mutexes is calculated from the + number of mutexes needed by various subsystems and can be + adjusted using the <a href="../api_reference/C/mutexset_increment.html" class="olink">DB_ENV->mutex_set_increment()</a> method. </p> <p> - For applications using shared memory (that is, they do not specify - <a href="../api_reference/C/envopen.html#envopen_DB_PRIVATE" class="olink">DB_PRIVATE</a>), a maximum memory size for the main region must be - specified or left to default. The maximum memory size is specified - using the <a href="../api_reference/C/envset_memory_max.html" class="olink">DB_ENV->set_memory_max()</a> method. + For applications using shared memory (that is, they do not + specify <a href="../api_reference/C/envopen.html#envopen_DB_PRIVATE" class="olink">DB_PRIVATE</a>), a maximum memory size for the main + region must be specified or left to default. The maximum + memory size is specified using the <a href="../api_reference/C/envset_memory_max.html" class="olink">DB_ENV->set_memory_max()</a> method. </p> - <p> + <p> The amount of memory needed by an application is dependent on the resources that the application uses. For a very rough estimate, add all of the following together: @@ -90,37 +89,40 @@ <div class="orderedlist"> <ol type="1"> <li> - <p> - The environment has an overhead of about 80 kilobytes - without statistics enabled or 250 kilobytes with statistics - enabled. + <p> + The environment has an overhead of about 80 + kilobytes without statistics enabled or 250 kilobytes + with statistics enabled. </p> </li> <li> <p> - Identify the amount of space you require for your locks: + Identify the amount of space you require for your + locks: </p> <div class="orderedlist"> <ol type="a"> <li> - <p> - Estimate the number of threads of control that will - simultaneously access the environment. + <p> + Estimate the number of threads of control + that will simultaneously access the + environment. </p> </li> <li> - <p> - Estimate the number of concurrency locks that, on average, - will be required by each thread. For information on - sizing concurrency locks, see - <a class="xref" href="lock_max.html" title="Configuring locking: sizing the system">Configuring locking: sizing the system</a>. + <p> + Estimate the number of concurrency locks + that, on average, will be required by each + thread. For information on sizing concurrency + locks, see <a class="xref" href="lock_max.html" title="Configuring locking: sizing the system">Configuring locking: sizing the + system</a>. </p> </li> <li> - <p> - Multiply these two numbers, then multiply by 1/2 to - arrive at the number of kilobytes required to - service your locks. + <p> + Multiply these two numbers, then multiply + by 1/2 to arrive at the number of kilobytes + required to service your locks. </p> </li> </ol> @@ -128,44 +130,45 @@ </li> <li> <p> - Estimate the number of open database handles you will use - at any given time. For each database handle, there is an - overhead of about 1/2 kilobyte. + Estimate the number of open database handles you + will use at any given time. For each database handle, + there is an overhead of about 1/2 kilobyte. </p> </li> <li> <p> - Add 1 kilobyte for each active transaction. + Add 1 kilobyte for each active transaction. </p> </li> </ol> </div> <p> Note that these are very rough guidelines. It is best to - overestimate the needs of your applications, because if the memory - allocation is exhausted the application must be shutdown to - increase the allocation. + overestimate the needs of your applications, because if the + memory allocation is exhausted the application must be + shutdown to increase the allocation. </p> <p> The estimate for maximum memory need not be exact. In most - situations there is little penalty for over estimating. For systems - using memory mapped files for the shared environment, this only - allocates the address space in the process to hold the maximum - memory. The backing file will only be extended as needed. For - systems running with <a href="../api_reference/C/envopen.html#envopen_DB_PRIVATE" class="olink">DB_PRIVATE</a> specified, the maximum memory - serves only as a limit and memory is allocated from the process - data space as needed. No maximum need be set for private - environments. + situations there is little penalty for over estimating. For + systems using memory mapped files for the shared environment, + this only allocates the address space in the process to hold + the maximum memory. The backing file will only be extended as + needed. For systems running with <a href="../api_reference/C/envopen.html#envopen_DB_PRIVATE" class="olink">DB_PRIVATE</a> specified, the + maximum memory serves only as a limit and memory is allocated + from the process data space as needed. No maximum need be set + for private environments. </p> - <p> - For locking and thread information, groups of objects are allocated - when needed so that there is less contention in the allocator - during performance critical operations. Once allocated to a - particular use, this memory will only be used for that structure. - To avoid runtime contention, or to ensure a minimum number of a - particular type of object, the <a href="../api_reference/C/envset_memory_init.html" class="olink">DB_ENV->set_memory_init()</a> method can be - used. This method can set the initial numbers of particular types - of structures to allocate at environment creation time. + <p> + For locking and thread information, groups of objects are + allocated when needed so that there is less contention in the + allocator during performance critical operations. Once + allocated to a particular use, this memory will only be used + for that structure. To avoid runtime contention, or to ensure + a minimum number of a particular type of object, the + <a href="../api_reference/C/envset_memory_init.html" class="olink">DB_ENV->set_memory_init()</a> method can be used. This method can set + the initial numbers of particular types of structures to + allocate at environment creation time. </p> </div> <div class="navfooter"> @@ -179,11 +182,13 @@ <td width="40%" align="right"> <a accesskey="n" href="env_open.html">Next</a></td> </tr> <tr> - <td width="40%" align="left" valign="top">Creating a database environment </td> + <td width="40%" align="left" valign="top">Creating a database + environment </td> <td width="20%" align="center"> <a accesskey="h" href="index.html">Home</a> </td> - <td width="40%" align="right" valign="top"> Opening databases within the environment</td> + <td width="40%" align="right" valign="top"> Opening databases within the + environment</td> </tr> </table> </div> |