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<div class="section-link"><a href="api-sync-behavior.html#api-sync-behavior">1. API synchronization behavior </a></div>
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<div class="section-link"><a href="stream-sync-behavior.html#stream-sync-behavior">2. Stream synchronization behavior</a></div>
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<div class="section-link"><a href="group__CUDA__INITIALIZE.html#group__CUDA__INITIALIZE">3.3. Initialization</a></div>
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<div class="section-link"><a href="group__CUDA__DEVICE__DEPRECATED.html#group__CUDA__DEVICE__DEPRECATED">3.6. Device Management [DEPRECATED]</a></div>
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<div class="section-link"><a href="group__CUDA__MEM.html#group__CUDA__MEM">3.10. Memory Management</a></div>
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<div class="section-link"><a href="group__CUDA__UNIFIED.html#group__CUDA__UNIFIED">3.11. Unified Addressing</a></div>
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<div class="section-link"><a href="group__CUDA__TEXREF.html#group__CUDA__TEXREF">3.17. Texture Reference Management</a></div>
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<div class="section-link"><a href="group__CUDA__GRAPHICS.html#group__CUDA__GRAPHICS">3.23. Graphics Interoperability</a></div>
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<div class="section-link"><a href="annotated.html#annotated">4. Data Structures</a></div>
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<article id="contents">
<div class="topic nested1" id="api-sync-behavior"><a name="api-sync-behavior" shape="rect">
<!-- --></a><h2 class="topictitle2">1. API synchronization behavior </h2>
<div class="body refbody">
<div class="section">
<p class="p">The API provides memcpy/memset functions in both synchronous and asynchronous forms, the latter having an "Async"
suffix. This is a misnomer as each function may exhibit synchronous or asynchronous behavior depending on the
arguments passed to the function. In the reference documentation, each memcpy function is categorized as synchronous
or asynchronous, corresponding to the definitions below.
</p>
</div>
<div class="section" id="api-sync-behavior__memcpy"><a name="api-sync-behavior__memcpy" shape="rect">
<!-- --></a><h2 class="title sectiontitle">Memcpy</h2>
<p class="p">The API provides memcpy/memset functions in both synchronous and asynchronous forms, the latter having an "Async" suffix.
This is a misnomer as each function may exhibit synchronous or asynchronous behavior depending on the arguments passed to
the function. In the reference documentation, each memcpy function is categorized as synchronous or asynchronous, corresponding
to the definitions below.
</p>
<p class="p apiDesc_subtitle" id="api-sync-behavior__memcpy-sync"><a name="api-sync-behavior__memcpy-sync" shape="rect">
<!-- --></a><strong class="ph b">Synchronous</strong></p>
<div class="p">
<ol class="ol">
<li class="li">
<p class="p">All transfers involving Unified Memory regions are fully synchronous with respect to the host.</p>
<p class="p"></p>
</li>
<li class="li">
<p class="p">For transfers from pageable host memory to device memory, a stream sync is performed before the copy is initiated. The function
will return once the pageable buffer has been copied to the staging memory for DMA transfer to device memory, but the DMA
to final destination may not have completed.
</p>
<p class="p"></p>
</li>
<li class="li">
<p class="p">For transfers from pinned host memory to device memory, the function is synchronous with respect to the host.</p>
<p class="p"></p>
</li>
<li class="li">
<p class="p">For transfers from device to either pageable or pinned host memory, the function returns only once the copy has completed.</p>
<p class="p"></p>
</li>
<li class="li">
<p class="p">For transfers from device memory to device memory, no host-side synchronization is performed.</p>
<p class="p"></p>
</li>
<li class="li">
<p class="p">For transfers from any host memory to any host memory, the function is fully synchronous with respect to the host. </p>
</li>
</ol>
</div>
<p class="p apiDesc_subtitle" id="api-sync-behavior__memcpy-async"><a name="api-sync-behavior__memcpy-async" shape="rect">
<!-- --></a><strong class="ph b">Asynchronous</strong></p>
<div class="p">
<ol class="ol">
<li class="li">
<p class="p">For transfers from pageable host memory to device memory, host memory is copied to a staging buffer immediately (no device
synchronization is performed). The function will return once the pageable buffer has been copied to the staging memory. The
DMA transfer to final destination may not have completed.
</p>
<p class="p"></p>
</li>
<li class="li">
<p class="p">For transfers between pinned host memory and device memory, the function is fully asynchronous.</p>
<p class="p"></p>
</li>
<li class="li">
<p class="p">For transfers from device memory to pageable host memory, the function will return only once the copy has completed.</p>
<p class="p"></p>
</li>
<li class="li">
<p class="p">For all other transfers, the function is fully asynchronous. If pageable memory must first be staged to pinned memory, this
will be handled asynchronously with a worker thread.
</p>
<p class="p"></p>
</li>
<li class="li">
<p class="p">For transfers from any host memory to any host memory, the function is fully synchronous with respect to the host. </p>
</li>
</ol>
</div>
</div>
<div class="section" id="api-sync-behavior__memset"><a name="api-sync-behavior__memset" shape="rect">
<!-- --></a><h2 class="title sectiontitle">Memset</h2>
<p class="p">The synchronous memset functions are asynchronous with respect to the host except when the target is pinned host memory or
a Unified Memory region, in which case they are fully synchronous. The Async versions are always asynchronous with respect
to the host.
</p>
</div>
<div class="section" id="api-sync-behavior__kernel-launch-details"><a name="api-sync-behavior__kernel-launch-details" shape="rect">
<!-- --></a><h2 class="title sectiontitle">Kernel Launches</h2>
<p class="p">Kernel launches are asynchronous with respect to the host. Details of concurrent kernel execution and data transfers can be
found in the CUDA Programmers Guide.
</p>
</div>
</div>
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