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71 lines
2.8 KiB
Markdown
71 lines
2.8 KiB
Markdown
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<!---
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Copyright (C) 2023 Intel Corporation
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SPDX-License-Identifier: MIT
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-->
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# Sysman Memory Bandwidth
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* [Overview](#Overview)
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* [Interfaces](#Interfaces)
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* [Known Issues and Limitations](#Known-Issues-and-Limitations)
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# Overview
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`zesMemoryGetBandwidth` exposes memory read, write counters and timestamp. The expectation is these
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counters are monotonically increasing and user can get bandwidth information using two snapshots of
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the read and write counters taken at different instances. However, the counters could overflow
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depending on underlying width of the counter presented by the hardware, and currently there is no
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mechanism with which user can detect these overflows. Therefore `zexSysmanMemoryGetBandwidth` is
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introduced to resolve this problem it takes care of overflow internally.
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`zexSysmanMemoryGetBandwidth` takes duration as input argument and provides reads and write counter
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values that elapsed in that duration. This interface blocks host thread progress for the duration
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specified by the user.
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To calculate the bandwidth using `zexSysmanMemoryGetBandwidth` use the formula
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`Bandwidth = (Readcounters + WriteCounters) / duration`
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# Interfaces
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```cpp
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///////////////////////////////////////////////////////////////////////////////
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/// @brief Get memory bandwidth
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///
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/// @details
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/// - The application may call this function from simultaneous threads.
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/// - The implementation of this function should be lock-free.
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///
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/// @returns
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/// - ::ZE_RESULT_SUCCESS
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/// - ::ZE_RESULT_ERROR_UNINITIALIZED
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/// - ::ZE_RESULT_ERROR_DEVICE_LOST
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/// - ::ZE_RESULT_ERROR_OUT_OF_HOST_MEMORY
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/// - ::ZE_RESULT_ERROR_OUT_OF_DEVICE_MEMORY
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/// - ::ZE_RESULT_ERROR_INVALID_NULL_HANDLE
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/// + `nullptr == hMemory`
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/// - ::ZE_RESULT_ERROR_INVALID_NULL_POINTER
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/// + `nullptr == pBandwidth`
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/// - ::ZE_RESULT_ERROR_INSUFFICIENT_PERMISSIONS
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/// + User does not have permissions to query this telemetry.
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ze_result_t ZE_APICALL
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zexSysmanMemoryGetBandwidth(
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zes_mem_handle_t hMemory, ///<[in] Handleforthecomponent.
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uint64_t *pReadCounters, ///<[out] Total bytes read from memory in duration
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uint64_t *pWriteCounters, ///<[out] Total bytes written to memory in duration
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uint64_t *pMaxBandwidth, ///<[out] Maximum bandwidth in units of bytes/sec
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uint64_t duration ///<[in] duration in milliseconds
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);
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```
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```cpp
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typedef ze_result_t (*pFnzexSysmanMemoryGetBandwidth)(zes_mem_handle_t, uint64 *, uint64 *, uint64 *, uint64);
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...
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pFnzexSysmanMemoryGetBandwidth zexSysmanMemoryGetBandwidth = nullptr;
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ze_result_t res = zeDriverGetExtensionFunctionAddress(hDriver, "zexSysmanMemoryGetBandwidth", reinterpret_cast<void **>(&zexSysmanMemoryGetBandwidth)));
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```
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# Known Issues and Limitations
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* Implemented and validation only on Xe HPC (PVC).
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