https://community.intel.com/t5/Software-Tuning-Performance/What-is-an-unknown-data-source/m-p/1131170#M6407 <P>The Intel manual mentions that some of the performance events exclude "unknown data source." These include the following events on Broadwell:</P><P>MEM_LOAD_UOPS_RETIRED.L1_MISS, MEM_LOAD_UOPS_RETIRED.L2_MISS, and MEM_LOAD_UOPS_RETIRED.L3_MISS.</P><P>and the following events on Haswell:</P><P>MEM_LOAD_UOPS_RETIRED.L2_MISS and MEM_LOAD_UOPS_RETIRED.L3_MISS.</P><P>and the MEM_LOAD_UOPS_RETIRED.L2_MISS event on Ivy Bridge.</P><P>There are apparently no "unknown data sources" on Skylake.</P><P>(1) What is an unknown data source?</P><P>(2) When and why unknown data sources occur?</P><P>(3) Does MEM_UOPS_RETIRED.ALL_LOADS count unknown data sources?</P><P>(4) Are there really no unknown data sources on Skylake or are they counted by the events?</P><P>(5) Why does MEM_LOAD_UOPS_RETIRED.L1_MISS include unknown data sources on Ivy Bridge and Haswell but not on Broadwell? Why does MEM_LOAD_UOPS_RETIRED.LLC_MISS include unknown data sources on Ivy Bridge but not on Haswell and Broadwell?</P><P>(6) The online documentation (https://download.01.org/perfmon/index/) also says that some of the cache hit events also exclude unknown data source on some of these microarchitectures. What does that mean? How can a cache hit have an unknown data source?</P><P>I find all of this very confusing.</P> Fri, 19 Apr 2019 19:22:33 GMT HadiBrais 2019-04-19T19:22:33Z https://community.intel.com/t5/Software-Tuning-Performance/What-is-an-unknown-data-source/m-p/1131170#M6407 <P>The Intel manual mentions that some of the performance events exclude "unknown data source." These include the following events on Broadwell:</P><P>MEM_LOAD_UOPS_RETIRED.L1_MISS, MEM_LOAD_UOPS_RETIRED.L2_MISS, and MEM_LOAD_UOPS_RETIRED.L3_MISS.</P><P>and the following events on Haswell:</P><P>MEM_LOAD_UOPS_RETIRED.L2_MISS and MEM_LOAD_UOPS_RETIRED.L3_MISS.</P><P>and the MEM_LOAD_UOPS_RETIRED.L2_MISS event on Ivy Bridge.</P><P>There are apparently no "unknown data sources" on Skylake.</P><P>(1) What is an unknown data source?</P><P>(2) When and why unknown data sources occur?</P><P>(3) Does MEM_UOPS_RETIRED.ALL_LOADS count unknown data sources?</P><P>(4) Are there really no unknown data sources on Skylake or are they counted by the events?</P><P>(5) Why does MEM_LOAD_UOPS_RETIRED.L1_MISS include unknown data sources on Ivy Bridge and Haswell but not on Broadwell? Why does MEM_LOAD_UOPS_RETIRED.LLC_MISS include unknown data sources on Ivy Bridge but not on Haswell and Broadwell?</P><P>(6) The online documentation (https://download.01.org/perfmon/index/) also says that some of the cache hit events also exclude unknown data source on some of these microarchitectures. What does that mean? How can a cache hit have an unknown data source?</P><P>I find all of this very confusing.</P> Fri, 19 Apr 2019 19:22:33 GMT https://community.intel.com/t5/Software-Tuning-Performance/What-is-an-unknown-data-source/m-p/1131170#M6407 HadiBrais 2019-04-19T19:22:33Z