AVX2 and AVX512* off by default to prevent frequency scaling #8376
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As discussed in open-mpi#8334 the intensive use of AVX2 and AVX512 will lead to a significant frequency scaling, with drastic impact on application performance. Until a better way to prevent this come up, we decided to artificially disable support for AVX2 and AVX512. The support for AVX2 and AVX512 can be enabled by users via the corresponding MCA parameter (op_avx_support). Signed-off-by: George Bosilca <[email protected]>
…thers not Signed-off-by: Jeff Squyres <[email protected]>
MCA enums make it easier for users to see/set MCA flag values. For example, ompi_output shows all the valid values: ``` $ ompi_info --all --parsable | grep _avx_ mca:op:avx:param:op_avx_available:value:SSE,SSE2,SSE3,SSE4.1,AVX mca:op:avx:param:op_avx_available:source:default mca:op:avx:param:op_avx_available:status:read-only mca:op:avx:param:op_avx_available:level:4 mca:op:avx:param:op_avx_available:help:Level of SSE/MMX/AVX support available mca:op:avx:param:op_avx_available:enumerator:value:1:SSE mca:op:avx:param:op_avx_available:enumerator:value:2:SSE2 mca:op:avx:param:op_avx_available:enumerator:value:4:SSE3 mca:op:avx:param:op_avx_available:enumerator:value:8:SSE4.1 mca:op:avx:param:op_avx_available:enumerator:value:16:AVX mca:op:avx:param:op_avx_available:enumerator:value:32:AVX2 mca:op:avx:param:op_avx_available:enumerator:value:256:AVX512F mca:op:avx:param:op_avx_available:enumerator:value:512:AVX512BW mca:op:avx:param:op_avx_available:deprecated:no mca:op:avx:param:op_avx_available:type:int mca:op:avx:param:op_avx_available:disabled:false mca:op:avx:param:op_avx_support:value:SSE,SSE2,SSE3,SSE4.1,AVX mca:op:avx:param:op_avx_support:source:default mca:op:avx:param:op_avx_support:status:writeable mca:op:avx:param:op_avx_support:level:4 mca:op:avx:param:op_avx_support:help:Level of SSE/MMX/AVX support to be used, capped by the local architecture capabilities mca:op:avx:param:op_avx_support:enumerator:value:1:SSE mca:op:avx:param:op_avx_support:enumerator:value:2:SSE2 mca:op:avx:param:op_avx_support:enumerator:value:4:SSE3 mca:op:avx:param:op_avx_support:enumerator:value:8:SSE4.1 mca:op:avx:param:op_avx_support:enumerator:value:16:AVX mca:op:avx:param:op_avx_support:enumerator:value:32:AVX2 mca:op:avx:param:op_avx_support:enumerator:value:256:AVX512F mca:op:avx:param:op_avx_support:enumerator:value:512:AVX512BW mca:op:avx:param:op_avx_support:deprecated:no mca:op:avx:param:op_avx_support:type:int mca:op:avx:param:op_avx_support:disabled:false ``` Signed-off-by: Jeff Squyres <[email protected]>
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@bosilca I pushed two additional commits; let's talk through these today on the call. |
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Based on the fact that we were unable to get a good understanding on when and what to restrict, we decided to close this PR without merging, leaving the AVX support on everywhere. @jsquyres commits adding the available and supported flags, and the user-friendly use of the MCA enum flags will have their own PR. |
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As discussed in #8334 the intensive use of AVX2 and AVX512 will lead to a
significant frequency scaling, with drastic impact on application performance.
Until a better way to prevent this come up, we decided to artificially disable
support for AVX2 and AVX512.
The support for AVX2 and AVX512 can be enabled by users via the corresponding
MCA parameter (op_avx_support).
Signed-off-by: George Bosilca [email protected]