Profiling
Quick profiling in your terminal
Note
This is only meant to be used for quick profiling or programmatically accessing the profiling results. For more detailed and GUI friendly profiling proceed to the next section.
Simply replace the use of Base.@time or Base.@timed with Reactant.Profiler.@time or Reactant.Profiler.@timed. We will automatically compile the function if it is not already a Reactant compiled function (with sync=true).
julia
using Reactant
x = Reactant.to_rarray(randn(Float32, 100, 2))
W = Reactant.to_rarray(randn(Float32, 10, 100))
b = Reactant.to_rarray(randn(Float32, 10))
linear(x, W, b) = (W * x) .+ b
Reactant.@time linear(x, W, b)┌ Debug: Profiling directory: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_vks1pR
└ @ Reactant.Profiler ~/work/Reactant.jl/Reactant.jl/src/Profiler.jl:626
WARNING: All log messages before absl::InitializeLog() is called are written to STDERR
I0000 00:00:1790329079.683149 4205 profiler_session.cc:171] Profiler session initializing.
I0000 00:00:1790329079.683201 4205 profiler_session.cc:186] Profiler session started.
I0000 00:00:1790329079.683519 4205 profiler_session.cc:134] Profiler session collecting data.
I0000 00:00:1790329079.717279 4205 save_profile.cc:205] Collecting XSpace to repository: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_vks1pR/plugins/profile/2026_09_25_09_37_59/runnervmtr4k5.xplane.pb
I0000 00:00:1790329079.718338 4205 save_profile.cc:178] Creating directory: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_vks1pR/plugins/profile/2026_09_25_09_37_59
I0000 00:00:1790329079.718460 4205 save_profile.cc:184] Dumped gzipped tool data for trace.json.gz to /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_vks1pR/plugins/profile/2026_09_25_09_37_59/runnervmtr4k5.trace.json.gz
I0000 00:00:1790329079.718490 4205 profiler_session.cc:217] Profiler session tear down.
┌ Debug: Starting XProf gRPC server...
└ @ Reactant.Profiler ~/work/Reactant.jl/Reactant.jl/src/Profiler.jl:598
┌ Debug: Initializing XProf stubs for worker service at 0.0.0.0:42699
└ @ Reactant.Profiler ~/work/Reactant.jl/Reactant.jl/src/Profiler.jl:397
I0000 00:00:1790329079.733973 4205 stub_factory.cc:163] Created gRPC channel for address: 0.0.0.0:42699
┌ Debug: Starting XProf gRPC server on port 42699
└ @ Reactant.Profiler ~/work/Reactant.jl/Reactant.jl/src/Profiler.jl:413
I0000 00:00:1790329079.734377 4205 grpc_server.cc:94] Server listening on 0.0.0.0:42699 with max_concurrent_requests 1
I0000 00:00:1790329079.743721 4205 xplane_to_tools_data_with_profile_processor.cc:142] serving tool: memory_profile with options: {} using ProfileProcessor session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_vks1pR/plugins/profile/2026_09_25_09_37_59
I0000 00:00:1790329079.743733 4205 xplane_to_tools_data_with_profile_processor.cc:165] Using local processing for tool: memory_profile
I0000 00:00:1790329079.743737 4205 memory_profile_processor.cc:47] Processing memory profile for host: runnervmtr4k5
I0000 00:00:1790329079.744217 4205 xplane_to_tools_data_with_profile_processor.cc:170] Total time for tool memory_profile: 491.834us session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_vks1pR/plugins/profile/2026_09_25_09_37_59
I0000 00:00:1790329079.753603 4205 xplane_to_tools_data_with_profile_processor.cc:142] serving tool: op_profile with options: {} using ProfileProcessor session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_vks1pR/plugins/profile/2026_09_25_09_37_59
I0000 00:00:1790329079.753614 4205 xplane_to_tools_data_with_profile_processor.cc:165] Using local processing for tool: op_profile
I0000 00:00:1790329079.753618 4205 multi_xplanes_to_op_stats.cc:118] ConvertMultiXSpaceToCombinedOpStatsWithCache: Started
I0000 00:00:1790329079.753655 4205 multi_xplanes_to_op_stats.cc:134] ConvertMultiXSpaceToCombinedOpStatsWithCache: Cache miss, calling ConvertMultiXSpacesToCombinedOpStats
I0000 00:00:1790329079.753658 4205 multi_xplanes_to_op_stats.cc:45] ConvertMultiXSpacesToCombinedOpStats: Started. Number of XSpaces: 1
I0000 00:00:1790329079.753661 4205 multi_xplanes_to_op_stats.cc:55] ConvertMultiXSpacesToCombinedOpStats: Starting to process XSpace 0/1
I0000 00:00:1790329079.753899 4205 derived_timeline.cc:693] GenerateDerivedTimeLines: creating derived_timeline_trace_events XprofThreadPoolExecutor
I0000 00:00:1790329079.753908 4205 xprof_thread_pool_executor.cc:22] Creating derived_timeline_trace_events XprofThreadPoolExecutor with 4 threads.
I0000 00:00:1790329079.754131 4205 derived_timeline.cc:705] GenerateDerivedTimeLines: waiting for derived_timeline_trace_events threads to join
I0000 00:00:1790329079.754429 4205 derived_timeline.cc:709] GenerateDerivedTimeLines: derived_timeline_trace_events threads joined successfully
I0000 00:00:1790329079.823395 4205 derived_timeline.cc:758] GenerateDerivedTimeLines: creating ProcessTensorCorePlanes XprofThreadPoolExecutor
I0000 00:00:1790329079.827848 4205 xprof_thread_pool_executor.cc:22] Creating ProcessTensorCorePlanes XprofThreadPoolExecutor with 4 threads.
I0000 00:00:1790329079.828040 4205 derived_timeline.cc:769] GenerateDerivedTimeLines: waiting for ProcessTensorCorePlanes threads to join
I0000 00:00:1790329079.828368 4205 derived_timeline.cc:772] GenerateDerivedTimeLines: ProcessTensorCorePlanes threads joined successfully
I0000 00:00:1790329079.931887 4205 xplane_to_op_stats.cc:405] ConvertXSpaceToOpStats: creating op_stats_threads XprofThreadPoolExecutor
I0000 00:00:1790329079.938443 4205 xprof_thread_pool_executor.cc:22] Creating op_stats_threads XprofThreadPoolExecutor with 4 threads.
I0000 00:00:1790329079.938800 4205 xplane_to_op_stats.cc:461] ConvertXSpaceToOpStats: Scheduled 0 OpMetricsDb generation tasks.
I0000 00:00:1790329079.939379 4205 xplane_to_op_stats.cc:417] ConvertXSpaceToOpStats: Combining 0 op_metrics_dbs.
I0000 00:00:1790329079.939394 4205 xplane_to_op_stats.cc:422] ConvertXSpaceToOpStats: Finished combining op_metrics_dbs.
I0000 00:00:1790329079.951261 4205 xplane_to_op_stats.cc:687] ConvertXSpaceToOpStats: Final OpStats size: 240 bytes (0.000228882 MiB).
I0000 00:00:1790329079.971312 4205 multi_xplanes_to_op_stats.cc:67] ConvertMultiXSpacesToCombinedOpStats: Finished processing XSpace 0.
I0000 00:00:1790329079.971883 4205 multi_xplanes_to_op_stats.cc:72] ConvertMultiXSpacesToCombinedOpStats: Finished extracting all 1 OpStats. Time: 218.228905ms
I0000 00:00:1790329079.971893 4205 multi_xplanes_to_op_stats.cc:85] ConvertMultiXSpacesToCombinedOpStats: Starting ComputeStepIntersectionToMergeOpStats.
I0000 00:00:1790329079.971897 4205 multi_xplanes_to_op_stats.cc:94] ConvertMultiXSpacesToCombinedOpStats: Finished ComputeStepIntersectionToMergeOpStats in 2.364us
I0000 00:00:1790329079.971899 4205 multi_xplanes_to_op_stats.cc:99] ConvertMultiXSpacesToCombinedOpStats: Starting CombineAllOpStats.
I0000 00:00:1790329079.971906 4205 multi_xplanes_to_op_stats.cc:106] ConvertMultiXSpacesToCombinedOpStats: Finished CombineAllOpStats in 5us
I0000 00:00:1790329079.971908 4205 multi_xplanes_to_op_stats.cc:109] ConvertMultiXSpacesToCombinedOpStats: Overall Finished in 218.250154ms
I0000 00:00:1790329079.971911 4205 multi_xplanes_to_op_stats.cc:138] ConvertMultiXSpaceToCombinedOpStatsWithCache: Starting to write cache file.
I0000 00:00:1790329079.972015 4205 multi_xplanes_to_op_stats.cc:145] ConvertMultiXSpaceToCombinedOpStatsWithCache: Finished writing cache file.
I0000 00:00:1790329079.972019 4205 multi_xplanes_to_op_stats.cc:149] ConvertMultiXSpaceToCombinedOpStatsWithCache: Overall Finished in 218.402127ms
I0000 00:00:1790329079.972185 4205 xplane_to_tools_data_with_profile_processor.cc:170] Total time for tool op_profile: 218.577263ms session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_vks1pR/plugins/profile/2026_09_25_09_37_59
┌ Debug: `op_profile` data missing keys for metrics
│ data_available_keys =
│ KeySet for a JSON.Object{String, Any} with 4 entries. Keys:
│ "byProgram"
│ "deviceType"
│ "byProgramExcludeIdle"
│ "aggDvfsTimeScaleMultiplier"
│ by_program_available_keys =
│ KeySet for a JSON.Object{String, Any} with 3 entries. Keys:
│ "name"
│ "children"
│ "numChildren"
└ @ Reactant.Profiler ~/work/Reactant.jl/Reactant.jl/src/Profiler.jl:828
I0000 00:00:1790329080.236921 4205 xplane_to_tools_data_with_profile_processor.cc:142] serving tool: overview_page with options: {} using ProfileProcessor session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_vks1pR/plugins/profile/2026_09_25_09_37_59
I0000 00:00:1790329080.236943 4205 xplane_to_tools_data_with_profile_processor.cc:165] Using local processing for tool: overview_page
I0000 00:00:1790329080.236946 4205 overview_page_processor.cc:84] OverviewPageProcessor::ProcessSession: Started
I0000 00:00:1790329080.236949 4205 overview_page_processor.cc:86] OverviewPageProcessor::ProcessSession: Starting ConvertMultiXSpaceToCombinedOpStatsWithCache
I0000 00:00:1790329080.236951 4205 multi_xplanes_to_op_stats.cc:118] ConvertMultiXSpaceToCombinedOpStatsWithCache: Started
I0000 00:00:1790329080.237009 4205 multi_xplanes_to_op_stats.cc:126] ConvertMultiXSpaceToCombinedOpStatsWithCache: Cache hit, reading binary proto
I0000 00:00:1790329080.237059 4205 multi_xplanes_to_op_stats.cc:131] ConvertMultiXSpaceToCombinedOpStatsWithCache: Finished reading cache file.
I0000 00:00:1790329080.237062 4205 multi_xplanes_to_op_stats.cc:149] ConvertMultiXSpaceToCombinedOpStatsWithCache: Overall Finished in 111.738us
I0000 00:00:1790329080.237087 4205 overview_page_processor.cc:90] OverviewPageProcessor::ProcessSession: Starting ConvertOpStatsToOverviewPage
I0000 00:00:1790329080.237097 4205 op_stats_to_overview_page.cc:388] ConvertOpStatsToOverviewPage: Starting ComputeRunEnvironment
I0000 00:00:1790329080.237103 4205 op_stats_to_overview_page.cc:393] ConvertOpStatsToOverviewPage: Starting ComputeAnalysisResult
I0000 00:00:1790329080.237107 4205 op_stats_to_overview_page.cc:396] ConvertOpStatsToOverviewPage: Starting ConvertOpStatsToInputPipelineAnalysis
I0000 00:00:1790329080.237266 4205 op_stats_to_overview_page.cc:401] ConvertOpStatsToOverviewPage: Starting ComputeBottleneckAnalysis
I0000 00:00:1790329080.237273 4205 op_stats_to_overview_page.cc:407] ConvertOpStatsToOverviewPage: Starting ComputeGenericRecommendation
I0000 00:00:1790329080.237373 4205 op_stats_to_overview_page.cc:412] ConvertOpStatsToOverviewPage: Starting SetCommonRecommendation
I0000 00:00:1790329080.237385 4205 op_stats_to_overview_page.cc:425] ConvertOpStatsToOverviewPage: Starting PopulateOverviewDiagnostics
I0000 00:00:1790329080.237388 4205 op_stats_to_overview_page.cc:429] ConvertOpStatsToOverviewPage: Starting setting utilizations
I0000 00:00:1790329080.237390 4205 op_stats_to_overview_page.cc:435] ConvertOpStatsToOverviewPage: Overall Finished in 293.425us
I0000 00:00:1790329080.237392 4205 overview_page_processor.cc:94] OverviewPageProcessor::ProcessSession: Not a training run, Starting to convert inference stats.
I0000 00:00:1790329080.237399 4205 xprof_thread_pool_executor.cc:22] Creating ConvertMultiXSpaceToInferenceStats XprofThreadPoolExecutor with 1 threads.
I0000 00:00:1790329080.238760 4205 overview_page_processor.cc:99] OverviewPageProcessor::ProcessSession: Starting to compute InferenceLatency
I0000 00:00:1790329080.238768 4205 overview_page_processor.cc:104] OverviewPageProcessor::ProcessSession: Starting to serialize OverviewPage toJson
I0000 00:00:1790329080.238988 4205 overview_page_processor.cc:107] OverviewPageProcessor::ProcessSession: Starting to set Output
I0000 00:00:1790329080.238995 4205 overview_page_processor.cc:109] OverviewPageProcessor::ProcessSession: Overall Finished in 2.049779ms
I0000 00:00:1790329080.239008 4205 xplane_to_tools_data_with_profile_processor.cc:170] Total time for tool overview_page: 2.069886ms session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_vks1pR/plugins/profile/2026_09_25_09_37_59
runtime: 0.00026364s
compile time: 0.62444080sjulia
Reactant.@timed nrepeat=100 linear(x, W, b)AggregateProfilingResult(
runtime = 0.00003906s,
compile_time = 0.10783698s, )Note that the information returned depends on the backend. Specifically CUDA and TPU backends provide more detailed information regarding memory usage and allocation (something like the following will be displayed on GPUs):
julia
AggregateProfilingResult(
runtime = 0.00003829s,
compile_time = 2.18053260s, # time spent compiling by Reactant
GPU_0_bfc = MemoryProfileSummary(
peak_bytes_usage_lifetime = 64.010 MiB, # peak memory usage over the entire program (lifetime of memory allocator)
peak_stats = MemoryAggregationStats(
stack_reserved_bytes = 0 bytes, # memory usage by stack reservation
heap_allocated_bytes = 30.750 KiB, # memory usage by heap allocation
free_memory_bytes = 23.518 GiB, # free memory available for allocation or reservation
fragmentation = 0.514931, # fragmentation of memory within [0, 1]
peak_bytes_in_use = 30.750 KiB # The peak memory usage over the entire program
)
peak_stats_time = 0.04975365s,
memory_capacity = 23.518 GiB # memory capacity of the allocator
)
flops = FlopsSummary(
Flops = 2.8369974648038653e-9, # [flops / (peak flops * program time)], capped at 1.0
UncappedFlops = 2.8369974648038653e-9,
RawFlops = 4060.0, # Total FLOPs performed
BF16Flops = 4060.0, # Total FLOPs Normalized to the bf16 (default) devices peak bandwidth
RawTime = 0.00040298422s, # Raw time in seconds
RawFlopsRate = 1.0074836180930361e7, # Raw FLOPs rate in FLOPs/seconds
BF16FlopsRate = 1.0074836180930361e7, # BF16 FLOPs rate in FLOPs/seconds
)
)Additionally for GPUs and TPUs, we can use the Reactant.@profile macro to profile the function and get information regarding each of the kernels executed.
julia
Reactant.@profile linear(x, W, b)┌ Debug: Profiling directory: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_NrjY9K
└ @ Reactant.Profiler ~/work/Reactant.jl/Reactant.jl/src/Profiler.jl:626
I0000 00:00:1790329081.140309 4205 profiler_session.cc:171] Profiler session initializing.
I0000 00:00:1790329081.140513 4205 profiler_session.cc:186] Profiler session started.
I0000 00:00:1790329081.140612 4205 profiler_session.cc:134] Profiler session collecting data.
I0000 00:00:1790329081.171276 4205 save_profile.cc:205] Collecting XSpace to repository: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_NrjY9K/plugins/profile/2026_09_25_09_38_01/runnervmtr4k5.xplane.pb
I0000 00:00:1790329081.171939 4205 save_profile.cc:178] Creating directory: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_NrjY9K/plugins/profile/2026_09_25_09_38_01
I0000 00:00:1790329081.172058 4205 save_profile.cc:184] Dumped gzipped tool data for trace.json.gz to /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_NrjY9K/plugins/profile/2026_09_25_09_38_01/runnervmtr4k5.trace.json.gz
I0000 00:00:1790329081.172102 4205 profiler_session.cc:217] Profiler session tear down.
I0000 00:00:1790329081.172181 4205 xplane_to_tools_data_with_profile_processor.cc:142] serving tool: memory_profile with options: {} using ProfileProcessor session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_NrjY9K/plugins/profile/2026_09_25_09_38_01
I0000 00:00:1790329081.172187 4205 xplane_to_tools_data_with_profile_processor.cc:165] Using local processing for tool: memory_profile
I0000 00:00:1790329081.172189 4205 memory_profile_processor.cc:47] Processing memory profile for host: runnervmtr4k5
I0000 00:00:1790329081.172481 4205 xplane_to_tools_data_with_profile_processor.cc:170] Total time for tool memory_profile: 298.916us session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_NrjY9K/plugins/profile/2026_09_25_09_38_01
I0000 00:00:1790329081.172510 4205 xplane_to_tools_data_with_profile_processor.cc:142] serving tool: op_profile with options: {} using ProfileProcessor session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_NrjY9K/plugins/profile/2026_09_25_09_38_01
I0000 00:00:1790329081.172514 4205 xplane_to_tools_data_with_profile_processor.cc:165] Using local processing for tool: op_profile
I0000 00:00:1790329081.172516 4205 multi_xplanes_to_op_stats.cc:118] ConvertMultiXSpaceToCombinedOpStatsWithCache: Started
I0000 00:00:1790329081.172544 4205 multi_xplanes_to_op_stats.cc:134] ConvertMultiXSpaceToCombinedOpStatsWithCache: Cache miss, calling ConvertMultiXSpacesToCombinedOpStats
I0000 00:00:1790329081.172547 4205 multi_xplanes_to_op_stats.cc:45] ConvertMultiXSpacesToCombinedOpStats: Started. Number of XSpaces: 1
I0000 00:00:1790329081.172551 4205 multi_xplanes_to_op_stats.cc:55] ConvertMultiXSpacesToCombinedOpStats: Starting to process XSpace 0/1
I0000 00:00:1790329081.172756 4205 derived_timeline.cc:693] GenerateDerivedTimeLines: creating derived_timeline_trace_events XprofThreadPoolExecutor
I0000 00:00:1790329081.172764 4205 xprof_thread_pool_executor.cc:22] Creating derived_timeline_trace_events XprofThreadPoolExecutor with 4 threads.
I0000 00:00:1790329081.172967 4205 derived_timeline.cc:705] GenerateDerivedTimeLines: waiting for derived_timeline_trace_events threads to join
I0000 00:00:1790329081.173270 4205 derived_timeline.cc:709] GenerateDerivedTimeLines: derived_timeline_trace_events threads joined successfully
I0000 00:00:1790329081.236707 4205 derived_timeline.cc:758] GenerateDerivedTimeLines: creating ProcessTensorCorePlanes XprofThreadPoolExecutor
I0000 00:00:1790329081.240861 4205 xprof_thread_pool_executor.cc:22] Creating ProcessTensorCorePlanes XprofThreadPoolExecutor with 4 threads.
I0000 00:00:1790329081.241052 4205 derived_timeline.cc:769] GenerateDerivedTimeLines: waiting for ProcessTensorCorePlanes threads to join
I0000 00:00:1790329081.241310 4205 derived_timeline.cc:772] GenerateDerivedTimeLines: ProcessTensorCorePlanes threads joined successfully
I0000 00:00:1790329081.343305 4205 xplane_to_op_stats.cc:405] ConvertXSpaceToOpStats: creating op_stats_threads XprofThreadPoolExecutor
I0000 00:00:1790329081.349176 4205 xprof_thread_pool_executor.cc:22] Creating op_stats_threads XprofThreadPoolExecutor with 4 threads.
I0000 00:00:1790329081.349371 4205 xplane_to_op_stats.cc:461] ConvertXSpaceToOpStats: Scheduled 0 OpMetricsDb generation tasks.
I0000 00:00:1790329081.349684 4205 xplane_to_op_stats.cc:417] ConvertXSpaceToOpStats: Combining 0 op_metrics_dbs.
I0000 00:00:1790329081.349693 4205 xplane_to_op_stats.cc:422] ConvertXSpaceToOpStats: Finished combining op_metrics_dbs.
I0000 00:00:1790329081.360949 4205 xplane_to_op_stats.cc:687] ConvertXSpaceToOpStats: Final OpStats size: 282 bytes (0.000268936 MiB).
I0000 00:00:1790329081.381095 4205 multi_xplanes_to_op_stats.cc:67] ConvertMultiXSpacesToCombinedOpStats: Finished processing XSpace 0.
I0000 00:00:1790329081.381579 4205 multi_xplanes_to_op_stats.cc:72] ConvertMultiXSpacesToCombinedOpStats: Finished extracting all 1 OpStats. Time: 209.035879ms
I0000 00:00:1790329081.381587 4205 multi_xplanes_to_op_stats.cc:85] ConvertMultiXSpacesToCombinedOpStats: Starting ComputeStepIntersectionToMergeOpStats.
I0000 00:00:1790329081.381591 4205 multi_xplanes_to_op_stats.cc:94] ConvertMultiXSpacesToCombinedOpStats: Finished ComputeStepIntersectionToMergeOpStats in 2.435us
I0000 00:00:1790329081.381594 4205 multi_xplanes_to_op_stats.cc:99] ConvertMultiXSpacesToCombinedOpStats: Starting CombineAllOpStats.
I0000 00:00:1790329081.381600 4205 multi_xplanes_to_op_stats.cc:106] ConvertMultiXSpacesToCombinedOpStats: Finished CombineAllOpStats in 5.159us
I0000 00:00:1790329081.381602 4205 multi_xplanes_to_op_stats.cc:109] ConvertMultiXSpacesToCombinedOpStats: Overall Finished in 209.055856ms
I0000 00:00:1790329081.381605 4205 multi_xplanes_to_op_stats.cc:138] ConvertMultiXSpaceToCombinedOpStatsWithCache: Starting to write cache file.
I0000 00:00:1790329081.381719 4205 multi_xplanes_to_op_stats.cc:145] ConvertMultiXSpaceToCombinedOpStatsWithCache: Finished writing cache file.
I0000 00:00:1790329081.381722 4205 multi_xplanes_to_op_stats.cc:149] ConvertMultiXSpaceToCombinedOpStatsWithCache: Overall Finished in 209.206415ms
I0000 00:00:1790329081.381754 4205 xplane_to_tools_data_with_profile_processor.cc:170] Total time for tool op_profile: 209.243655ms session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_NrjY9K/plugins/profile/2026_09_25_09_38_01
┌ Debug: `op_profile` data missing keys for metrics
│ data_available_keys =
│ KeySet for a JSON.Object{String, Any} with 4 entries. Keys:
│ "byProgram"
│ "deviceType"
│ "byProgramExcludeIdle"
│ "aggDvfsTimeScaleMultiplier"
│ by_program_available_keys =
│ KeySet for a JSON.Object{String, Any} with 3 entries. Keys:
│ "name"
│ "children"
│ "numChildren"
└ @ Reactant.Profiler ~/work/Reactant.jl/Reactant.jl/src/Profiler.jl:828
I0000 00:00:1790329081.382193 4205 xplane_to_tools_data_with_profile_processor.cc:142] serving tool: overview_page with options: {} using ProfileProcessor session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_NrjY9K/plugins/profile/2026_09_25_09_38_01
I0000 00:00:1790329081.382202 4205 xplane_to_tools_data_with_profile_processor.cc:165] Using local processing for tool: overview_page
I0000 00:00:1790329081.382205 4205 overview_page_processor.cc:84] OverviewPageProcessor::ProcessSession: Started
I0000 00:00:1790329081.382207 4205 overview_page_processor.cc:86] OverviewPageProcessor::ProcessSession: Starting ConvertMultiXSpaceToCombinedOpStatsWithCache
I0000 00:00:1790329081.382208 4205 multi_xplanes_to_op_stats.cc:118] ConvertMultiXSpaceToCombinedOpStatsWithCache: Started
I0000 00:00:1790329081.382247 4205 multi_xplanes_to_op_stats.cc:126] ConvertMultiXSpaceToCombinedOpStatsWithCache: Cache hit, reading binary proto
I0000 00:00:1790329081.382288 4205 multi_xplanes_to_op_stats.cc:131] ConvertMultiXSpaceToCombinedOpStatsWithCache: Finished reading cache file.
I0000 00:00:1790329081.382291 4205 multi_xplanes_to_op_stats.cc:149] ConvertMultiXSpaceToCombinedOpStatsWithCache: Overall Finished in 83.125us
I0000 00:00:1790329081.382293 4205 overview_page_processor.cc:90] OverviewPageProcessor::ProcessSession: Starting ConvertOpStatsToOverviewPage
I0000 00:00:1790329081.382296 4205 op_stats_to_overview_page.cc:388] ConvertOpStatsToOverviewPage: Starting ComputeRunEnvironment
I0000 00:00:1790329081.382300 4205 op_stats_to_overview_page.cc:393] ConvertOpStatsToOverviewPage: Starting ComputeAnalysisResult
I0000 00:00:1790329081.382304 4205 op_stats_to_overview_page.cc:396] ConvertOpStatsToOverviewPage: Starting ConvertOpStatsToInputPipelineAnalysis
I0000 00:00:1790329081.382341 4205 op_stats_to_overview_page.cc:401] ConvertOpStatsToOverviewPage: Starting ComputeBottleneckAnalysis
I0000 00:00:1790329081.382345 4205 op_stats_to_overview_page.cc:407] ConvertOpStatsToOverviewPage: Starting ComputeGenericRecommendation
I0000 00:00:1790329081.382350 4205 op_stats_to_overview_page.cc:412] ConvertOpStatsToOverviewPage: Starting SetCommonRecommendation
I0000 00:00:1790329081.382356 4205 op_stats_to_overview_page.cc:425] ConvertOpStatsToOverviewPage: Starting PopulateOverviewDiagnostics
I0000 00:00:1790329081.382358 4205 op_stats_to_overview_page.cc:429] ConvertOpStatsToOverviewPage: Starting setting utilizations
I0000 00:00:1790329081.382359 4205 op_stats_to_overview_page.cc:435] ConvertOpStatsToOverviewPage: Overall Finished in 64.099us
I0000 00:00:1790329081.382361 4205 overview_page_processor.cc:94] OverviewPageProcessor::ProcessSession: Not a training run, Starting to convert inference stats.
I0000 00:00:1790329081.382368 4205 xprof_thread_pool_executor.cc:22] Creating ConvertMultiXSpaceToInferenceStats XprofThreadPoolExecutor with 1 threads.
I0000 00:00:1790329081.383667 4205 overview_page_processor.cc:99] OverviewPageProcessor::ProcessSession: Starting to compute InferenceLatency
I0000 00:00:1790329081.383675 4205 overview_page_processor.cc:104] OverviewPageProcessor::ProcessSession: Starting to serialize OverviewPage toJson
I0000 00:00:1790329081.383891 4205 overview_page_processor.cc:107] OverviewPageProcessor::ProcessSession: Starting to set Output
I0000 00:00:1790329081.383897 4205 overview_page_processor.cc:109] OverviewPageProcessor::ProcessSession: Overall Finished in 1.693418ms
I0000 00:00:1790329081.383909 4205 xplane_to_tools_data_with_profile_processor.cc:170] Total time for tool overview_page: 1.711441ms session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_NrjY9K/plugins/profile/2026_09_25_09_38_01
I0000 00:00:1790329081.476201 4205 xplane_to_tools_data_with_profile_processor.cc:142] serving tool: kernel_stats with options: {} using ProfileProcessor session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_NrjY9K/plugins/profile/2026_09_25_09_38_01
I0000 00:00:1790329081.476227 4205 xplane_to_tools_data_with_profile_processor.cc:165] Using local processing for tool: kernel_stats
I0000 00:00:1790329081.476231 4205 multi_xplanes_to_op_stats.cc:118] ConvertMultiXSpaceToCombinedOpStatsWithCache: Started
I0000 00:00:1790329081.476286 4205 multi_xplanes_to_op_stats.cc:126] ConvertMultiXSpaceToCombinedOpStatsWithCache: Cache hit, reading binary proto
I0000 00:00:1790329081.476332 4205 multi_xplanes_to_op_stats.cc:131] ConvertMultiXSpaceToCombinedOpStatsWithCache: Finished reading cache file.
I0000 00:00:1790329081.476334 4205 multi_xplanes_to_op_stats.cc:149] ConvertMultiXSpaceToCombinedOpStatsWithCache: Overall Finished in 103.963us
I0000 00:00:1790329081.476392 4205 xplane_to_tools_data_with_profile_processor.cc:170] Total time for tool kernel_stats: 170.707us session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_NrjY9K/plugins/profile/2026_09_25_09_38_01
I0000 00:00:1790329081.597712 4205 xplane_to_tools_data_with_profile_processor.cc:142] serving tool: framework_op_stats with options: {} using ProfileProcessor session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_NrjY9K/plugins/profile/2026_09_25_09_38_01
I0000 00:00:1790329081.597738 4205 xplane_to_tools_data_with_profile_processor.cc:165] Using local processing for tool: framework_op_stats
I0000 00:00:1790329081.597741 4205 multi_xplanes_to_op_stats.cc:118] ConvertMultiXSpaceToCombinedOpStatsWithCache: Started
I0000 00:00:1790329081.597794 4205 multi_xplanes_to_op_stats.cc:126] ConvertMultiXSpaceToCombinedOpStatsWithCache: Cache hit, reading binary proto
I0000 00:00:1790329081.597839 4205 multi_xplanes_to_op_stats.cc:131] ConvertMultiXSpaceToCombinedOpStatsWithCache: Finished reading cache file.
I0000 00:00:1790329081.597841 4205 multi_xplanes_to_op_stats.cc:149] ConvertMultiXSpaceToCombinedOpStatsWithCache: Overall Finished in 100.697us
I0000 00:00:1790329081.597973 4205 xplane_to_tools_data_with_profile_processor.cc:170] Total time for tool framework_op_stats: 239.044us session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_NrjY9K/plugins/profile/2026_09_25_09_38_01
╔================================================================================╗
║ SUMMARY ║
╚================================================================================╝
AggregateProfilingResult(
runtime = 0.00007434s,
compile_time = 0.10195899s, # time spent compiling by Reactant
)On GPUs this would look something like the following:
julia
╔================================================================================╗
║ KERNEL STATISTICS ║
╚================================================================================╝
┌───────────────────┬─────────────┬────────────────┬──────────────┬──────────────┬──────────────┬──────────────┬───────────┬──────────┬────────────┬─────────────┐
│ Kernel Name │ Occurrences │ Total Duration │ Avg Duration │ Min Duration │ Max Duration │ Static Shmem │ Block Dim │ Grid Dim │ TensorCore │ Occupancy % │
├───────────────────┼─────────────┼────────────────┼──────────────┼──────────────┼──────────────┼──────────────┼───────────┼──────────┼────────────┼─────────────┤
│ gemm_fusion_dot_1 │ 1 │ 0.00000250s │ 0.00000250s │ 0.00000250s │ 0.00000250s │ 2.000 KiB │ 64,1,1 │ 1,1,1 │ ✗ │ 100.0% │
│ loop_add_fusion │ 1 │ 0.00000131s │ 0.00000131s │ 0.00000131s │ 0.00000131s │ 0 bytes │ 20,1,1 │ 1,1,1 │ ✗ │ 31.2% │
└───────────────────┴─────────────┴────────────────┴──────────────┴──────────────┴──────────────┴──────────────┴───────────┴──────────┴────────────┴─────────────┘
╔================================================================================╗
║ FRAMEWORK OP STATISTICS ║
╚================================================================================╝
┌───────────────────┬─────────┬─────────────┬─────────────┬─────────────────┬───────────────┬──────────┬───────────┬──────────────┬──────────┐
│ Operation │ Type │ Host/Device │ Occurrences │ Total Self-Time │ Avg Self-Time │ Device % │ Memory BW │ FLOP Rate │ Bound By │
├───────────────────┼─────────┼─────────────┼─────────────┼─────────────────┼───────────────┼──────────┼───────────┼──────────────┼──────────┤
│ gemm_fusion_dot.1 │ Unknown │ Device │ 1 │ 0.00000250s │ 0.00000250s │ 65.55% │ 1.82 GB/s │ 1.6 GFLOP/s │ HBM │
│ +/add │ add │ Device │ 1 │ 0.00000131s │ 0.00000131s │ 34.45% │ 0.14 GB/s │ 0.05 GFLOP/s │ HBM │
└───────────────────┴─────────┴─────────────┴─────────────┴─────────────────┴───────────────┴──────────┴───────────┴──────────────┴──────────┘
╔================================================================================╗
║ SUMMARY ║
╚================================================================================╝
AggregateProfilingResult(
runtime = 0.00005622s,
compile_time = 2.32802137s, # time spent compiling by Reactant
GPU_0_bfc = MemoryProfileSummary(
peak_bytes_usage_lifetime = 64.010 MiB, # peak memory usage over the entire program (lifetime of memory allocator)
peak_stats = MemoryAggregationStats(
stack_reserved_bytes = 0 bytes, # memory usage by stack reservation
heap_allocated_bytes = 81.750 KiB, # memory usage by heap allocation
free_memory_bytes = 23.518 GiB, # free memory available for allocation or reservation
fragmentation = 0.514564, # fragmentation of memory within [0, 1]
peak_bytes_in_use = 81.750 KiB # The peak memory usage over the entire program
)
peak_stats_time = 0.00608052s,
memory_capacity = 23.518 GiB # memory capacity of the allocator
)
flops = FlopsSummary(
Flops = 2.033375207640664e-8, # [flops / (peak flops * program time)], capped at 1.0
UncappedFlops = 2.033375207640664e-8,
RawFlops = 4060.0, # Total FLOPs performed
BF16Flops = 4060.0, # Total FLOPs Normalized to the bf16 (default) devices peak bandwidth
RawTime = 0.00005622s, # Raw time in seconds
RawFlopsRate = 7.220987105380169e7, # Raw FLOPs rate in FLOPs/seconds
BF16FlopsRate = 7.220987105380169e7, # BF16 FLOPs rate in FLOPs/seconds
)
)Capturing traces
When running Reactant, it is possible to capture traces using the XLA profiler. These traces can provide information about where the XLA specific parts of program spend time during compilation or execution. Note that tracing and compilation happen on the CPU even though the final execution is aimed to run on another device such as GPU or TPU. Therefore, including tracing and compilation in a trace will create annotations on the CPU.
Let's setup a simple function which we can then profile
julia
using Reactant
x = Reactant.to_rarray(randn(Float32, 100, 2))
W = Reactant.to_rarray(randn(Float32, 10, 100))
b = Reactant.to_rarray(randn(Float32, 10))
linear(x, W, b) = (W * x) .+ blinear (generic function with 1 method)The profiler can be accessed using the Reactant.with_profiler function.
julia
Reactant.with_profiler("./") do
mylinear = Reactant.@compile linear(x, W, b)
mylinear(x, W, b)
end10×2 ConcretePJRTArray{Float32,2}:
1.57471 -4.85204
-6.22777 15.892
-12.4305 -12.759
-3.19677 -0.324637
9.5225 -7.87654
-23.1625 -1.14386
20.736 3.67129
-16.6076 4.51058
5.73719 -0.707212
-0.905483 0.80356Running this function should create a folder called plugins in the folder provided to Reactant.with_profiler which will contain the trace files. The traces can then be visualized in different ways.
Note
For more insights about the current state of Reactant, it is possible to fetch device information about allocations using the Reactant.XLA.allocatorstats function.
Perfetto UI
The first and easiest way to visualize a captured trace is to use the online perfetto.dev tool. Reactant.with_profiler has a keyword parameter called create_perfetto_link which will create a usable perfetto URL for the generated trace. The function will block execution until the URL has been clicked and the trace is visualized. The URL only works once.
julia
Reactant.with_profiler("./"; create_perfetto_link=true) do
mylinear = Reactant.@compile linear(x, W, b)
mylinear(x, W, b)
endNote
It is recommended to use the Chrome browser to open the perfetto URL.
XProf
XProf is a complete web UI to analyze the log files captured by Reactant. It can be installed in the following manner:
bash
pip install xprof # or xprof-nightlyLaunching xprof is then as simple as:
bash
xprof --logdir=./which will then make the xprof interface available on port :8791 by default.
Tensorboard
Another option to visualize the generated trace files is to use the tensorboard profiler plugin. The tensorboard viewer can offer more details than the timeline view such as visualization for compute graphs.
First install tensorboard and its profiler plugin:
bash
pip install tensorboard tensorboard-plugin-profileAnd then run the following in the folder where the plugins folder was generated:
bash
tensorboard --logdir ./Adding Custom Annotations
By default, the traces contain only information captured from within XLA. The Reactant.Profiler.annotate function can be used to annotate traces for Julia code evaluated during tracing.
julia
Reactant.Profiler.annotate("my_annotation") do
# Do things...
endThe added annotations will be captured in the traces and can be seen in the different viewers along with the default XLA annotations. When the profiler is not activated, then the custom annotations have no effect and can therefore always be activated.