xnu-2422.1.72.tar.gz

[apple/xnu.git] / osfmk / man / memory_object_perf_info.html

<h2>memory_object_perf_info</h2>
<hr>
<p>
<strong>Structure</strong> - Specifies a memory object's attributes with respect to performance.
<h3>SYNOPSIS</h3>
<pre>
<strong>struct  memory_object_perf_info</strong>
<strong>{</strong>
        <strong>vm_offset_t</strong>      <var>cluster_size</var><strong>;</strong>
        <strong>boolean_t</strong>    <var>may_cache_object</var><strong>;</strong>
<strong>};</strong>

<strong>typedef struct memory_object_perf_info* memory_object_perf_info_t;</strong>
</pre>
<h3>FIELDS</h3>
<dl>
<dt> <var>cluster_size</var>
<dd>
Preferred cluster size (in bytes) for the memory object.  This helps to 
determine how many pages are transferred in individual data request 
and return messages.
<p>
<dt> <var>may_cache_object</var>
<dd>
Cache indicator.  If true, the kernel can cache data associated with the 
memory object (keep the memory object active) even if no virtual 
memory references to it remain.
</dl>
<h3>DESCRIPTION</h3>
<p>
The <strong>memory_object_perf_info</strong> structure
defines a memory object's character with respect to performance.
<h3>NOTES</h3>
<p>
Sharing cached data among all the clients of a memory object can have a major 
impact on performance, especially if it can be extended across successive, as 
well as concurrent, uses.  For example, the memory objects that represent
program images can be used regularly by different programs. 
By retaining the data 
for these memory objects in cache, the number of secondary storage accesses 
can be reduced significantly.
<h3>RELATED INFORMATION</h3>
<p>
Functions:
<a href="MO_get_attributes.html"><strong>memory_object_get_attributes</strong></a>,
<a href="MO_change_attributes.html"><strong>memory_object_change_attributes</strong></a>,
<a href="vm_region.html"><strong>vm_region</strong></a>,
<a href="memory_object_synchronize.html"><strong>memory_object_synchronize</strong></a>,
<a href="VSD_memory_manager.html"><strong>vm_set_default_memory_manager</strong></a>,
<a href="vm_msync.html"><strong>vm_msync</strong></a>.
<p>
Structures:
<a href="memory_object_attr_info.html"><strong>memory_object_attr_info</strong></a>.