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| <title>clSVMAlloc</title> |
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| <body> |
| <div class="refentry"> |
| <a id="id-1"></a> |
| <div class="titlepage"></div> |
| <div xmlns="" class="refnamediv"> |
| <a xmlns="http://www.w3.org/1999/xhtml" id="clSVMAlloc"></a> |
| <h1> |
| clSVMAlloc |
| </h1> |
| <p> |
| Allocates a shared virtual memory (SVM) buffer that can be shared by the host and all devices in an OpenCL context that support shared virtual memory. |
| </p> |
| </div> |
| <div class="refsynopsisdiv"> |
| <h2></h2> |
| <div class="funcsynopsis"> |
| <table xmlns="" border="0" summary="Function synopsis" cellspacing="0" cellpadding="0"> |
| <tr valign="bottom"> |
| <td> |
| <code xmlns="http://www.w3.org/1999/xhtml" class="funcdef"> |
| <a class="link" href="abstractDataTypes.html" target="pagedisplay">void</a> <strong class="fsfunc"> * clSVMAlloc</strong> |
| (</code> |
| <td><a xmlns="http://www.w3.org/1999/xhtml" class="link" href="abstractDataTypes.html" target="pagedisplay">cl_context</a> <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">context</var>, </td> |
| </td> |
| </tr> |
| <tr valign="top"> |
| <td> </td> |
| <td><a xmlns="http://www.w3.org/1999/xhtml" class="link" href="enums.html#cl_svm_mem_flags" target="pagedisplay">cl_svm_mem_flags</a> <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">flags</var>, </td> |
| </tr> |
| <tr valign="top"> |
| <td> </td> |
| <td><a xmlns="http://www.w3.org/1999/xhtml" class="link" href="scalarDataTypes.html" target="pagedisplay">size_t</a> <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">size</var>, </td> |
| </tr> |
| <tr valign="top"> |
| <td> </td> |
| <td><a xmlns="http://www.w3.org/1999/xhtml" class="link" href="scalarDataTypes.html" target="pagedisplay">cl_uint</a> <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">alignment</var><code>)</code></td> |
| </tr> |
| </table> |
| </div> |
| </div> |
| <div class="refsect1"> |
| <a id="parameters"></a> |
| <h2>Parameters</h2> |
| <div class="variablelist"> |
| <dl class="variablelist"> |
| <dt> |
| <span class="term"> |
| <code class="varname">context</code> |
| </span> |
| </dt> |
| <dd> |
| <p>A valid OpenCL context used to create the SVM buffer.</p> |
| </dd> |
| <dt> |
| <span class="term"> <code class="varname">flags</code> </span> |
| </dt> |
| <dd> |
| <p> |
| A bit-field that is used to specify |
| allocation and usage information. The following |
| table describes the possible values for <code class="varname">flags</code>. |
| </p> |
| <div class="informaltable"> |
| <table class="informaltable" border="1"> |
| <colgroup> |
| <col align="left" class="col1" /> |
| <col align="left" class="col2" /> |
| </colgroup> |
| <thead> |
| <tr> |
| <th align="left">cl_svm_mem_flags</th> |
| <th align="left">Description</th> |
| </tr> |
| </thead> |
| <tbody> |
| <tr> |
| <td align="left"> |
| <code class="constant">CL_MEM_READ_WRITE</code> |
| </td> |
| <td align="left"> |
| This flag specifies that the SVM buffer will be read |
| and written by a kernel. This is the default. |
| </td> |
| </tr> |
| <tr> |
| <td align="left"> |
| <code class="constant">CL_MEM_WRITE_ONLY</code> |
| </td> |
| <td align="left"> |
| <p> |
| This flag specifies that the SVM buffer will be written |
| but not read by a kernel. |
| </p> |
| <p> |
| Reading from a SVM buffer created with |
| <code class="constant">CL_MEM_WRITE_ONLY</code> inside a kernel is undefined. |
| </p> |
| <p> |
| <code class="constant">CL_MEM_READ_WRITE</code> and |
| <code class="constant">CL_MEM_WRITE_ONLY</code> are mutually exclusive. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td align="left"> |
| <code class="constant">CL_MEM_READ_ONLY</code> |
| </td> |
| <td align="left"> |
| <p> |
| This flag specifies that the SVM buffer object is a |
| read-only memory object when used inside a kernel. |
| </p> |
| <p> |
| Writing to a SVM buffer created with |
| <code class="constant">CL_MEM_READ_ONLY</code> inside a kernel is undefined. |
| </p> |
| <p> |
| <code class="constant">CL_MEM_READ_WRITE</code> or <code class="constant">CL_MEM_WRITE_ONLY</code> and |
| <code class="constant">CL_MEM_READ_ONLY</code> are mutually exclusive. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td align="left"> |
| <code class="constant">CL_MEM_SVM_FINE_GRAIN_BUFFER</code> |
| </td> |
| <td align="left"> |
| This specifies that the application wants the OpenCL |
| implementation to do a fine-grained allocation. |
| </td> |
| </tr> |
| <tr> |
| <td align="left"> |
| <code class="constant">CL_MEM_SVM_ATOMICS</code> |
| </td> |
| <td align="left"> |
| This flag is valid only if |
| <code class="constant">CL_MEM_SVM_FINE_GRAIN_BUFFER</code> is specified in |
| <code class="varname">flags</code>. It is used to indicate that SVM atomic |
| operations can control visibility of memory accesses |
| in this SVM buffer. |
| </td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| </dd> |
| <dt> |
| <span class="term"> |
| <code class="varname">size</code> |
| </span> |
| </dt> |
| <dd> |
| <p>The size in bytes of the SVM buffer to be allocated.</p> |
| </dd> |
| <dt> |
| <span class="term"> |
| <code class="varname">alignment</code> |
| </span> |
| </dt> |
| <dd> |
| <p> |
| The minimum alignment in bytes that is required for |
| the newly created buffer’s |
| memory region. It must be a power of two up to the |
| largest data type supported by the OpenCL |
| device. For the full profile, the largest data type |
| is <span class="type">long16</span>. For the embedded profile, it is |
| <span class="type">long16</span> if the device supports 64-bit |
| integers; otherwise it is <span class="type">int16</span>. If |
| alignment is 0, a |
| default alignment will be used that is equal to |
| the size of largest data type supported by the |
| OpenCL implementation. |
| </p> |
| </dd> |
| </dl> |
| </div> |
| </div> |
| <div class="refsect1"> |
| <a id="notes"></a> |
| <h2>Notes</h2> |
| <p> |
| If <code class="constant">CL_MEM_SVM_FINE_GRAIN_BUFFER</code> is not |
| specified, the buffer can be created as a coarse |
| grained SVM allocation. Similarly, if <code class="constant">CL_MEM_SVM_ATOMICS</code> |
| is not specified, the buffer can be |
| created without support for SVM atomic |
| operations (refer to the OpenCL C++ kernel language and IL specifications). |
| </p> |
| <p> |
| Calling <code class="function">clSVMAlloc</code> does not itself |
| provide consistency for the shared memory region. When |
| the host can’t use the SVM atomic operations, it |
| must rely on OpenCL’s guaranteed memory |
| consistency at synchronization points. |
| </p> |
| <p> |
| For SVM to be used efficiently, the host and any |
| devices sharing a buffer containing virtual |
| memory pointers should have the same endianness. |
| If the context passed to <code class="function">clSVMAlloc</code> has |
| devices with mixed endianness and the OpenCL |
| implementation is unable to implement SVM |
| because of that mixed endianness, |
| <code class="function">clSVMAlloc</code> will fail and return NULL. |
| </p> |
| <p> |
| Although SVM is generally not supported for image objects, |
| <a class="citerefentry" href="clCreateImage.html"><span class="citerefentry"><span class="refentrytitle">clCreateImage</span></span></a> |
| may create an image from a buffer (a 1D image from a buffer |
| or a 2D image from buffer) if the buffer specified |
| in its image description parameter is a SVM |
| buffer. Such images have a linear memory |
| representation so their memory can be |
| shared using SVM. However, fine grained sharing and |
| atomics are not supported for image reads and writes in a kernel. |
| </p> |
| <p> |
| If <a class="citerefentry" href="clCreateBuffer.html"><span class="citerefentry"><span class="refentrytitle">clCreateBuffer</span></span></a> |
| is called with a pointer returned by |
| <code class="function">clSVMAlloc</code> as its |
| <code class="varname">host_ptr</code> argument, and |
| <code class="constant">CL_MEM_USE_HOST_PTR</code> is set in its <code class="varname">flags</code> argument, |
| <a class="citerefentry" href="clCreateBuffer.html"><span class="citerefentry"><span class="refentrytitle">clCreateBuffer</span></span></a> |
| will succeed and return a |
| valid non-zero buffer object as long as the <code class="varname">size</code> |
| argument to |
| <a class="citerefentry" href="clCreateBuffer.html"><span class="citerefentry"><span class="refentrytitle">clCreateBuffer</span></span></a> |
| is no larger than the |
| <code class="varname">size</code> argument passed in the original |
| <code class="function">clSVMAlloc</code> call. The new buffer object returned has the |
| shared memory as the underlying storage. Locations in |
| the buffer's underlying shared memory |
| can be operated on using atomic operations to the device's |
| level of support as defined in the |
| memory model. |
| </p> |
| </div> |
| <div class="refsect1"> |
| <a id="errors"></a> |
| <h2>Errors</h2> |
| <p> |
| Returns a valid non-NULL shared virtual memory address if the SVM buffer is |
| successfully allocated. Otherwise, like malloc, it returns a NULL pointer |
| value. <code class="function">clSVMAlloc</code> will fail if: |
| </p> |
| <div class="itemizedlist"> |
| <ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem" style="list-style-type: disc"><code class="varname">context</code> is not a valid context. |
| </li> |
| <li class="listitem" style="list-style-type: disc"><code class="varname">flags</code> does not contain |
| <code class="constant">CL_MEM_SVM_FINE_GRAIN_BUFFER</code> but does contain |
| <code class="constant">CL_MEM_SVM_ATOMICS</code>. |
| </li> |
| <li class="listitem" style="list-style-type: disc"> |
| Values specified in <code class="varname">flags</code> do not follow |
| rules described for supported values in the table above. |
| </li> |
| <li class="listitem" style="list-style-type: disc"><code class="constant">CL_MEM_SVM_FINE_GRAIN_BUFFER</code> or |
| <code class="constant">CL_MEM_SVM_ATOMICS</code> is specified in |
| <code class="varname">flags</code> and these are not supported |
| by at least one device in <code class="varname">context</code>. |
| </li> |
| <li class="listitem" style="list-style-type: disc"> |
| The values specified in <code class="varname">flags</code> are |
| not valid i.e. don’t match those defined in the table above. |
| </li> |
| <li class="listitem" style="list-style-type: disc"><code class="varname">size</code> is 0 or > <code class="constant">CL_DEVICE_MAX_MEM_ALLOC_SIZE</code> |
| value for any device in <code class="varname">context</code>. |
| </li> |
| <li class="listitem" style="list-style-type: disc"><code class="varname">alignment</code> is not a power of two |
| or the OpenCL implementation cannot support the |
| specified alignment for at least one device in <code class="varname">context</code>. |
| </li> |
| <li class="listitem" style="list-style-type: disc"> |
| There was a failure to allocate resources. |
| </li> |
| </ul> |
| </div> |
| </div> |
| <div class="refsect1"> |
| <a id="specification"></a> |
| <h2>Specification</h2> |
| <p> |
| <img src="pdficon_small1.gif" /> |
| |
| <a href="https://www.khronos.org/registry/cl/specs/opencl-2.1.pdf#namedest=clSVMAlloc" target="OpenCL Spec">OpenCL Specification</a> |
| </p> |
| </div> |
| <div class="refsect1"> |
| <a id="seealso"></a> |
| <h2>Also see</h2> |
| <p> |
| <a class="citerefentry" href="clSVMFree.html"><span class="citerefentry"><span class="refentrytitle">clSVMFree</span></span></a>, |
| <a class="citerefentry" href="sharedVirtualMemory.html"><span class="citerefentry"><span class="refentrytitle">Shared Virtual Memory Functions</span></span></a> |
| </p> |
| </div> |
| <div xmlns="" class="refsect3" lang="en" xml:lang="en"><a xmlns="http://www.w3.org/1999/xhtml" id="Copyright"></a><h4 xmlns="http://www.w3.org/1999/xhtml"></h4><img xmlns="http://www.w3.org/1999/xhtml" src="KhronosLogo.jpg" /><p xmlns="http://www.w3.org/1999/xhtml"></p>Copyright © 2007-2015 The Khronos Group Inc. |
| Permission is hereby granted, free of charge, to any person obtaining a |
| copy of this software and/or associated documentation files (the |
| "Materials"), to deal in the Materials without restriction, including |
| without limitation the rights to use, copy, modify, merge, publish, |
| distribute, sublicense, and/or sell copies of the Materials, and to |
| permit persons to whom the Materials are furnished to do so, subject to |
| the condition that this copyright notice and permission notice shall be included |
| in all copies or substantial portions of the Materials. |
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