{"push_id":2914130183,"size":1,"distinct_size":1,"ref":"refs/heads/_1_3__powerpc_powernv_npu_Reduce_eieio_usage_when_issuing_ATSD_invalidates_mbox_next","head":"af2007519322b68a68bf142f8a5b7e7d2448ff3b","before":"9eafdbb6999674b598a935d2f21c7efa904c4879","commits":[{"sha":"af2007519322b68a68bf142f8a5b7e7d2448ff3b","author":{"name":"Mark Hairgrove","email":"54959fc8b60e3604fe2c52d8937efb756b452305@nvidia.com"},"message":"powerpc/powernv/npu: Reduce eieio usage when issuing ATSD invalidates\n\nThere are two types of ATSDs issued to the NPU: invalidates targeting a\nspecific virtual address and invalidates targeting the whole address\nspace. In both cases prior to this change, the sequence was:\n\n    for each NPU\n        - Write the target address to the XTS_ATSD_AVA register\n        - EIEIO\n        - Write the launch value to issue the ATSD\n\nFirst, a target address is not required when invalidating the whole\naddress space, so that write and the EIEIO have been removed. The AP\n(size) field in the launch is not needed either.\n\nSecond, for per-address invalidates the above sequence is inefficient in\nthe common case of multiple NPUs because an EIEIO is issued per NPU. This\nunnecessarily forces the launches of later ATSDs to be ordered with the\nlaunches of earlier ones. The new sequence only issues a single EIEIO:\n\n    for each NPU\n        - Write the target address to the XTS_ATSD_AVA register\n    EIEIO\n    for each NPU\n        - Write the launch value to issue the ATSD\n\nPerformance results were gathered using a microbenchmark which creates a\n1G allocation then uses mprotect with PROT_NONE to trigger invalidates in\nstrides across the allocation.\n\nWith only a single NPU active (one GPU) the difference is in the noise for\nboth types of invalidates (+/-1%).\n\nWith two NPUs active (on a 6-GPU system) the effect is more noticeable:\n\n         mprotect rate (GB/s)\nStride   Before      After      Speedup\n64K         5.9        6.5          10%\n1M         31.2       33.4           7%\n2M         36.3       38.7           7%\n4M        322.6      356.7          11%\n\nSigned-off-by: Mark Hairgrove <mhairgrove@nvidia.com>","distinct":true,"url":"https://api.github.com/repos/ruscur/linux/commits/af2007519322b68a68bf142f8a5b7e7d2448ff3b"}]}
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