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_INVa4P
└ @ Reactant.Profiler ~/work/Reactant.jl/Reactant.jl/src/Profiler.jl:516
WARNING: All log messages before absl::InitializeLog() is called are written to STDERR
I0000 00:00:1773433311.507267 4143 profiler_session.cc:117] Profiler session initializing.
I0000 00:00:1773433311.507306 4143 profiler_session.cc:132] Profiler session started.
I0000 00:00:1773433311.507613 4143 profiler_session.cc:81] Profiler session collecting data.
I0000 00:00:1773433311.508175 4143 save_profile.cc:150] Collecting XSpace to repository: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_INVa4P/plugins/profile/2026_03_13_20_21_51/runnervm46oaq.xplane.pb
I0000 00:00:1773433311.508319 4143 save_profile.cc:123] Creating directory: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_INVa4P/plugins/profile/2026_03_13_20_21_51
I0000 00:00:1773433311.508440 4143 save_profile.cc:129] Dumped gzipped tool data for trace.json.gz to /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_INVa4P/plugins/profile/2026_03_13_20_21_51/runnervm46oaq.trace.json.gz
I0000 00:00:1773433311.508457 4143 profiler_session.cc:150] Profiler session tear down.
┌ Debug: Starting XProf gRPC server...
└ @ Reactant.Profiler ~/work/Reactant.jl/Reactant.jl/src/Profiler.jl:490
┌ Debug: Initializing XProf stubs for worker service at 0.0.0.0:38129
└ @ Reactant.Profiler ~/work/Reactant.jl/Reactant.jl/src/Profiler.jl:289
I0000 00:00:1773433311.523180 4143 stub_factory.cc:163] Created gRPC channel for address: 0.0.0.0:38129
┌ Debug: Starting XProf gRPC server on port 38129
└ @ Reactant.Profiler ~/work/Reactant.jl/Reactant.jl/src/Profiler.jl:305
I0000 00:00:1773433311.523634 4143 grpc_server.cc:94] Server listening on 0.0.0.0:38129 with max_concurrent_requests 1
I0000 00:00:1773433311.532373 4143 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_INVa4P/plugins/profile/2026_03_13_20_21_51
I0000 00:00:1773433311.532389 4143 xplane_to_tools_data_with_profile_processor.cc:165] Using local processing for tool: memory_profile
I0000 00:00:1773433311.532392 4143 memory_profile_processor.cc:47] Processing memory profile for host: runnervm46oaq
I0000 00:00:1773433311.532675 4143 xplane_to_tools_data_with_profile_processor.cc:170] Total time for tool memory_profile: 291.603us session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_INVa4P/plugins/profile/2026_03_13_20_21_51
I0000 00:00:1773433311.545539 4143 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_INVa4P/plugins/profile/2026_03_13_20_21_51
I0000 00:00:1773433311.545554 4143 xplane_to_tools_data_with_profile_processor.cc:165] Using local processing for tool: op_profile
I0000 00:00:1773433311.545557 4143 multi_xplanes_to_op_stats.cc:118] ConvertMultiXSpaceToCombinedOpStatsWithCache: Started
I0000 00:00:1773433311.545606 4143 multi_xplanes_to_op_stats.cc:134] ConvertMultiXSpaceToCombinedOpStatsWithCache: Cache miss, calling ConvertMultiXSpacesToCombinedOpStats
I0000 00:00:1773433311.545609 4143 multi_xplanes_to_op_stats.cc:45] ConvertMultiXSpacesToCombinedOpStats: Started. Number of XSpaces: 1
I0000 00:00:1773433311.545614 4143 multi_xplanes_to_op_stats.cc:55] ConvertMultiXSpacesToCombinedOpStats: Starting to process XSpace 0/1
I0000 00:00:1773433311.545724 4143 derived_timeline.cc:693] GenerateDerivedTimeLines: creating derived_timeline_trace_events XprofThreadPoolExecutor
I0000 00:00:1773433311.545733 4143 xprof_thread_pool_executor.cc:22] Creating derived_timeline_trace_events XprofThreadPoolExecutor with 4 threads.
I0000 00:00:1773433311.545988 4143 derived_timeline.cc:705] GenerateDerivedTimeLines: waiting for derived_timeline_trace_events threads to join
I0000 00:00:1773433311.546318 4143 derived_timeline.cc:709] GenerateDerivedTimeLines: derived_timeline_trace_events threads joined successfully
I0000 00:00:1773433311.546623 4143 derived_timeline.cc:758] GenerateDerivedTimeLines: creating ProcessTensorCorePlanes XprofThreadPoolExecutor
I0000 00:00:1773433311.546637 4143 xprof_thread_pool_executor.cc:22] Creating ProcessTensorCorePlanes XprofThreadPoolExecutor with 4 threads.
I0000 00:00:1773433311.546842 4143 derived_timeline.cc:769] GenerateDerivedTimeLines: waiting for ProcessTensorCorePlanes threads to join
I0000 00:00:1773433311.547112 4143 derived_timeline.cc:772] GenerateDerivedTimeLines: ProcessTensorCorePlanes threads joined successfully
I0000 00:00:1773433311.549642 4143 xplane_to_op_stats.cc:402] ConvertXSpaceToOpStats: creating op_stats_threads XprofThreadPoolExecutor
I0000 00:00:1773433311.549657 4143 xprof_thread_pool_executor.cc:22] Creating op_stats_threads XprofThreadPoolExecutor with 4 threads.
I0000 00:00:1773433311.549841 4143 xplane_to_op_stats.cc:458] ConvertXSpaceToOpStats: Scheduled 0 OpMetricsDb generation tasks.
I0000 00:00:1773433311.550127 4143 xplane_to_op_stats.cc:414] ConvertXSpaceToOpStats: Combining 0 op_metrics_dbs.
I0000 00:00:1773433311.550137 4143 xplane_to_op_stats.cc:419] ConvertXSpaceToOpStats: Finished combining op_metrics_dbs.
I0000 00:00:1773433311.550330 4143 xplane_to_op_stats.cc:684] ConvertXSpaceToOpStats: Final OpStats size: 220 bytes (0.000209808 MiB).
I0000 00:00:1773433311.550397 4143 multi_xplanes_to_op_stats.cc:67] ConvertMultiXSpacesToCombinedOpStats: Finished processing XSpace 0.
I0000 00:00:1773433311.550410 4143 multi_xplanes_to_op_stats.cc:72] ConvertMultiXSpacesToCombinedOpStats: Finished extracting all 1 OpStats. Time: 4.802416ms
I0000 00:00:1773433311.550416 4143 multi_xplanes_to_op_stats.cc:85] ConvertMultiXSpacesToCombinedOpStats: Starting ComputeStepIntersectionToMergeOpStats.
I0000 00:00:1773433311.550420 4143 multi_xplanes_to_op_stats.cc:94] ConvertMultiXSpacesToCombinedOpStats: Finished ComputeStepIntersectionToMergeOpStats in 1.473us
I0000 00:00:1773433311.550422 4143 multi_xplanes_to_op_stats.cc:99] ConvertMultiXSpacesToCombinedOpStats: Starting CombineAllOpStats.
I0000 00:00:1773433311.550426 4143 multi_xplanes_to_op_stats.cc:106] ConvertMultiXSpacesToCombinedOpStats: Finished CombineAllOpStats in 2.885us
I0000 00:00:1773433311.550429 4143 multi_xplanes_to_op_stats.cc:109] ConvertMultiXSpacesToCombinedOpStats: Overall Finished in 4.819898ms
I0000 00:00:1773433311.550432 4143 multi_xplanes_to_op_stats.cc:138] ConvertMultiXSpaceToCombinedOpStatsWithCache: Starting to write cache file.
I0000 00:00:1773433311.550510 4143 multi_xplanes_to_op_stats.cc:145] ConvertMultiXSpaceToCombinedOpStatsWithCache: Finished writing cache file.
I0000 00:00:1773433311.550515 4143 multi_xplanes_to_op_stats.cc:149] ConvertMultiXSpaceToCombinedOpStatsWithCache: Overall Finished in 4.958036ms
I0000 00:00:1773433311.550619 4143 xplane_to_tools_data_with_profile_processor.cc:170] Total time for tool op_profile: 5.069623ms session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_INVa4P/plugins/profile/2026_03_13_20_21_51
┌ 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:706
I0000 00:00:1773433311.815017 4143 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_INVa4P/plugins/profile/2026_03_13_20_21_51
I0000 00:00:1773433311.815038 4143 xplane_to_tools_data_with_profile_processor.cc:165] Using local processing for tool: overview_page
I0000 00:00:1773433311.815041 4143 overview_page_processor.cc:84] OverviewPageProcessor::ProcessSession: Started
I0000 00:00:1773433311.815044 4143 overview_page_processor.cc:86] OverviewPageProcessor::ProcessSession: Starting ConvertMultiXSpaceToCombinedOpStatsWithCache
I0000 00:00:1773433311.815046 4143 multi_xplanes_to_op_stats.cc:118] ConvertMultiXSpaceToCombinedOpStatsWithCache: Started
I0000 00:00:1773433311.815107 4143 multi_xplanes_to_op_stats.cc:126] ConvertMultiXSpaceToCombinedOpStatsWithCache: Cache hit, reading binary proto
I0000 00:00:1773433311.815158 4143 multi_xplanes_to_op_stats.cc:131] ConvertMultiXSpaceToCombinedOpStatsWithCache: Finished reading cache file.
I0000 00:00:1773433311.815161 4143 multi_xplanes_to_op_stats.cc:149] ConvertMultiXSpaceToCombinedOpStatsWithCache: Overall Finished in 114.683us
I0000 00:00:1773433311.815165 4143 overview_page_processor.cc:90] OverviewPageProcessor::ProcessSession: Starting ConvertOpStatsToOverviewPage
I0000 00:00:1773433311.815168 4143 op_stats_to_overview_page.cc:388] ConvertOpStatsToOverviewPage: Starting ComputeRunEnvironment
I0000 00:00:1773433311.815174 4143 op_stats_to_overview_page.cc:393] ConvertOpStatsToOverviewPage: Starting ComputeAnalysisResult
I0000 00:00:1773433311.815179 4143 op_stats_to_overview_page.cc:396] ConvertOpStatsToOverviewPage: Starting ConvertOpStatsToInputPipelineAnalysis
I0000 00:00:1773433311.815336 4143 op_stats_to_overview_page.cc:401] ConvertOpStatsToOverviewPage: Starting ComputeBottleneckAnalysis
I0000 00:00:1773433311.815344 4143 op_stats_to_overview_page.cc:407] ConvertOpStatsToOverviewPage: Starting ComputeGenericRecommendation
I0000 00:00:1773433311.815441 4143 op_stats_to_overview_page.cc:412] ConvertOpStatsToOverviewPage: Starting SetCommonRecommendation
I0000 00:00:1773433311.815452 4143 op_stats_to_overview_page.cc:425] ConvertOpStatsToOverviewPage: Starting PopulateOverviewDiagnostics
I0000 00:00:1773433311.815454 4143 op_stats_to_overview_page.cc:429] ConvertOpStatsToOverviewPage: Starting setting utilizations
I0000 00:00:1773433311.815456 4143 op_stats_to_overview_page.cc:435] ConvertOpStatsToOverviewPage: Overall Finished in 289.179us
I0000 00:00:1773433311.815459 4143 overview_page_processor.cc:94] OverviewPageProcessor::ProcessSession: Not a training run, Starting to convert inference stats.
I0000 00:00:1773433311.815467 4143 xprof_thread_pool_executor.cc:22] Creating ConvertMultiXSpaceToInferenceStats XprofThreadPoolExecutor with 1 threads.
I0000 00:00:1773433311.815905 4143 overview_page_processor.cc:99] OverviewPageProcessor::ProcessSession: Starting to compute InferenceLatency
I0000 00:00:1773433311.815915 4143 overview_page_processor.cc:104] OverviewPageProcessor::ProcessSession: Starting to serialize OverviewPage toJson
I0000 00:00:1773433311.816125 4143 overview_page_processor.cc:107] OverviewPageProcessor::ProcessSession: Starting to set Output
I0000 00:00:1773433311.816133 4143 overview_page_processor.cc:109] OverviewPageProcessor::ProcessSession: Overall Finished in 1.092125ms
I0000 00:00:1773433311.816145 4143 xplane_to_tools_data_with_profile_processor.cc:170] Total time for tool overview_page: 1.112192ms session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_INVa4P/plugins/profile/2026_03_13_20_21_51
runtime: 0.00024733s
compile time: 3.56487194sjulia
Reactant.@timed nrepeat=100 linear(x, W, b)AggregateProfilingResult(
runtime = 0.00002677s,
compile_time = 0.12766734s, )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_tulxb1
└ @ Reactant.Profiler ~/work/Reactant.jl/Reactant.jl/src/Profiler.jl:516
I0000 00:00:1773433312.546424 4143 profiler_session.cc:117] Profiler session initializing.
I0000 00:00:1773433312.546501 4143 profiler_session.cc:132] Profiler session started.
I0000 00:00:1773433312.546592 4143 profiler_session.cc:81] Profiler session collecting data.
I0000 00:00:1773433312.547013 4143 save_profile.cc:150] Collecting XSpace to repository: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_tulxb1/plugins/profile/2026_03_13_20_21_52/runnervm46oaq.xplane.pb
I0000 00:00:1773433312.547160 4143 save_profile.cc:123] Creating directory: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_tulxb1/plugins/profile/2026_03_13_20_21_52
I0000 00:00:1773433312.547274 4143 save_profile.cc:129] Dumped gzipped tool data for trace.json.gz to /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_tulxb1/plugins/profile/2026_03_13_20_21_52/runnervm46oaq.trace.json.gz
I0000 00:00:1773433312.547290 4143 profiler_session.cc:150] Profiler session tear down.
I0000 00:00:1773433312.547350 4143 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_tulxb1/plugins/profile/2026_03_13_20_21_52
I0000 00:00:1773433312.547356 4143 xplane_to_tools_data_with_profile_processor.cc:165] Using local processing for tool: memory_profile
I0000 00:00:1773433312.547358 4143 memory_profile_processor.cc:47] Processing memory profile for host: runnervm46oaq
I0000 00:00:1773433312.547490 4143 xplane_to_tools_data_with_profile_processor.cc:170] Total time for tool memory_profile: 137.927us session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_tulxb1/plugins/profile/2026_03_13_20_21_52
I0000 00:00:1773433312.547511 4143 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_tulxb1/plugins/profile/2026_03_13_20_21_52
I0000 00:00:1773433312.547515 4143 xplane_to_tools_data_with_profile_processor.cc:165] Using local processing for tool: op_profile
I0000 00:00:1773433312.547517 4143 multi_xplanes_to_op_stats.cc:118] ConvertMultiXSpaceToCombinedOpStatsWithCache: Started
I0000 00:00:1773433312.547547 4143 multi_xplanes_to_op_stats.cc:134] ConvertMultiXSpaceToCombinedOpStatsWithCache: Cache miss, calling ConvertMultiXSpacesToCombinedOpStats
I0000 00:00:1773433312.547550 4143 multi_xplanes_to_op_stats.cc:45] ConvertMultiXSpacesToCombinedOpStats: Started. Number of XSpaces: 1
I0000 00:00:1773433312.547553 4143 multi_xplanes_to_op_stats.cc:55] ConvertMultiXSpacesToCombinedOpStats: Starting to process XSpace 0/1
I0000 00:00:1773433312.547621 4143 derived_timeline.cc:693] GenerateDerivedTimeLines: creating derived_timeline_trace_events XprofThreadPoolExecutor
I0000 00:00:1773433312.547628 4143 xprof_thread_pool_executor.cc:22] Creating derived_timeline_trace_events XprofThreadPoolExecutor with 4 threads.
I0000 00:00:1773433312.547851 4143 derived_timeline.cc:705] GenerateDerivedTimeLines: waiting for derived_timeline_trace_events threads to join
I0000 00:00:1773433312.548139 4143 derived_timeline.cc:709] GenerateDerivedTimeLines: derived_timeline_trace_events threads joined successfully
I0000 00:00:1773433312.548467 4143 derived_timeline.cc:758] GenerateDerivedTimeLines: creating ProcessTensorCorePlanes XprofThreadPoolExecutor
I0000 00:00:1773433312.548484 4143 xprof_thread_pool_executor.cc:22] Creating ProcessTensorCorePlanes XprofThreadPoolExecutor with 4 threads.
I0000 00:00:1773433312.548632 4143 derived_timeline.cc:769] GenerateDerivedTimeLines: waiting for ProcessTensorCorePlanes threads to join
I0000 00:00:1773433312.548909 4143 derived_timeline.cc:772] GenerateDerivedTimeLines: ProcessTensorCorePlanes threads joined successfully
I0000 00:00:1773433312.549269 4143 xplane_to_op_stats.cc:402] ConvertXSpaceToOpStats: creating op_stats_threads XprofThreadPoolExecutor
I0000 00:00:1773433312.549287 4143 xprof_thread_pool_executor.cc:22] Creating op_stats_threads XprofThreadPoolExecutor with 4 threads.
I0000 00:00:1773433312.549440 4143 xplane_to_op_stats.cc:458] ConvertXSpaceToOpStats: Scheduled 0 OpMetricsDb generation tasks.
I0000 00:00:1773433312.549698 4143 xplane_to_op_stats.cc:414] ConvertXSpaceToOpStats: Combining 0 op_metrics_dbs.
I0000 00:00:1773433312.549708 4143 xplane_to_op_stats.cc:419] ConvertXSpaceToOpStats: Finished combining op_metrics_dbs.
I0000 00:00:1773433312.549870 4143 xplane_to_op_stats.cc:684] ConvertXSpaceToOpStats: Final OpStats size: 262 bytes (0.000249863 MiB).
I0000 00:00:1773433312.549940 4143 multi_xplanes_to_op_stats.cc:67] ConvertMultiXSpacesToCombinedOpStats: Finished processing XSpace 0.
I0000 00:00:1773433312.549965 4143 multi_xplanes_to_op_stats.cc:72] ConvertMultiXSpacesToCombinedOpStats: Finished extracting all 1 OpStats. Time: 2.417491ms
I0000 00:00:1773433312.549970 4143 multi_xplanes_to_op_stats.cc:85] ConvertMultiXSpacesToCombinedOpStats: Starting ComputeStepIntersectionToMergeOpStats.
I0000 00:00:1773433312.549973 4143 multi_xplanes_to_op_stats.cc:94] ConvertMultiXSpacesToCombinedOpStats: Finished ComputeStepIntersectionToMergeOpStats in 1.623us
I0000 00:00:1773433312.549976 4143 multi_xplanes_to_op_stats.cc:99] ConvertMultiXSpacesToCombinedOpStats: Starting CombineAllOpStats.
I0000 00:00:1773433312.549981 4143 multi_xplanes_to_op_stats.cc:106] ConvertMultiXSpacesToCombinedOpStats: Finished CombineAllOpStats in 3.417us
I0000 00:00:1773433312.549983 4143 multi_xplanes_to_op_stats.cc:109] ConvertMultiXSpacesToCombinedOpStats: Overall Finished in 2.433712ms
I0000 00:00:1773433312.549986 4143 multi_xplanes_to_op_stats.cc:138] ConvertMultiXSpaceToCombinedOpStatsWithCache: Starting to write cache file.
I0000 00:00:1773433312.550045 4143 multi_xplanes_to_op_stats.cc:145] ConvertMultiXSpaceToCombinedOpStatsWithCache: Finished writing cache file.
I0000 00:00:1773433312.550050 4143 multi_xplanes_to_op_stats.cc:149] ConvertMultiXSpaceToCombinedOpStatsWithCache: Overall Finished in 2.532847ms
I0000 00:00:1773433312.550071 4143 xplane_to_tools_data_with_profile_processor.cc:170] Total time for tool op_profile: 2.558955ms session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_tulxb1/plugins/profile/2026_03_13_20_21_52
┌ 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:706
I0000 00:00:1773433312.550373 4143 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_tulxb1/plugins/profile/2026_03_13_20_21_52
I0000 00:00:1773433312.550380 4143 xplane_to_tools_data_with_profile_processor.cc:165] Using local processing for tool: overview_page
I0000 00:00:1773433312.550383 4143 overview_page_processor.cc:84] OverviewPageProcessor::ProcessSession: Started
I0000 00:00:1773433312.550385 4143 overview_page_processor.cc:86] OverviewPageProcessor::ProcessSession: Starting ConvertMultiXSpaceToCombinedOpStatsWithCache
I0000 00:00:1773433312.550387 4143 multi_xplanes_to_op_stats.cc:118] ConvertMultiXSpaceToCombinedOpStatsWithCache: Started
I0000 00:00:1773433312.550421 4143 multi_xplanes_to_op_stats.cc:126] ConvertMultiXSpaceToCombinedOpStatsWithCache: Cache hit, reading binary proto
I0000 00:00:1773433312.550457 4143 multi_xplanes_to_op_stats.cc:131] ConvertMultiXSpaceToCombinedOpStatsWithCache: Finished reading cache file.
I0000 00:00:1773433312.550459 4143 multi_xplanes_to_op_stats.cc:149] ConvertMultiXSpaceToCombinedOpStatsWithCache: Overall Finished in 72.766us
I0000 00:00:1773433312.550462 4143 overview_page_processor.cc:90] OverviewPageProcessor::ProcessSession: Starting ConvertOpStatsToOverviewPage
I0000 00:00:1773433312.550464 4143 op_stats_to_overview_page.cc:388] ConvertOpStatsToOverviewPage: Starting ComputeRunEnvironment
I0000 00:00:1773433312.550469 4143 op_stats_to_overview_page.cc:393] ConvertOpStatsToOverviewPage: Starting ComputeAnalysisResult
I0000 00:00:1773433312.550472 4143 op_stats_to_overview_page.cc:396] ConvertOpStatsToOverviewPage: Starting ConvertOpStatsToInputPipelineAnalysis
I0000 00:00:1773433312.550501 4143 op_stats_to_overview_page.cc:401] ConvertOpStatsToOverviewPage: Starting ComputeBottleneckAnalysis
I0000 00:00:1773433312.550506 4143 op_stats_to_overview_page.cc:407] ConvertOpStatsToOverviewPage: Starting ComputeGenericRecommendation
I0000 00:00:1773433312.550511 4143 op_stats_to_overview_page.cc:412] ConvertOpStatsToOverviewPage: Starting SetCommonRecommendation
I0000 00:00:1773433312.550516 4143 op_stats_to_overview_page.cc:425] ConvertOpStatsToOverviewPage: Starting PopulateOverviewDiagnostics
I0000 00:00:1773433312.550519 4143 op_stats_to_overview_page.cc:429] ConvertOpStatsToOverviewPage: Starting setting utilizations
I0000 00:00:1773433312.550520 4143 op_stats_to_overview_page.cc:435] ConvertOpStatsToOverviewPage: Overall Finished in 56.445us
I0000 00:00:1773433312.550523 4143 overview_page_processor.cc:94] OverviewPageProcessor::ProcessSession: Not a training run, Starting to convert inference stats.
I0000 00:00:1773433312.550527 4143 xprof_thread_pool_executor.cc:22] Creating ConvertMultiXSpaceToInferenceStats XprofThreadPoolExecutor with 1 threads.
I0000 00:00:1773433312.550764 4143 overview_page_processor.cc:99] OverviewPageProcessor::ProcessSession: Starting to compute InferenceLatency
I0000 00:00:1773433312.550772 4143 overview_page_processor.cc:104] OverviewPageProcessor::ProcessSession: Starting to serialize OverviewPage toJson
I0000 00:00:1773433312.550981 4143 overview_page_processor.cc:107] OverviewPageProcessor::ProcessSession: Starting to set Output
I0000 00:00:1773433312.550991 4143 overview_page_processor.cc:109] OverviewPageProcessor::ProcessSession: Overall Finished in 608.233us
I0000 00:00:1773433312.551001 4143 xplane_to_tools_data_with_profile_processor.cc:170] Total time for tool overview_page: 623.591us session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_tulxb1/plugins/profile/2026_03_13_20_21_52
I0000 00:00:1773433312.644960 4143 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_tulxb1/plugins/profile/2026_03_13_20_21_52
I0000 00:00:1773433312.644993 4143 xplane_to_tools_data_with_profile_processor.cc:165] Using local processing for tool: kernel_stats
I0000 00:00:1773433312.644997 4143 multi_xplanes_to_op_stats.cc:118] ConvertMultiXSpaceToCombinedOpStatsWithCache: Started
I0000 00:00:1773433312.645059 4143 multi_xplanes_to_op_stats.cc:126] ConvertMultiXSpaceToCombinedOpStatsWithCache: Cache hit, reading binary proto
I0000 00:00:1773433312.645116 4143 multi_xplanes_to_op_stats.cc:131] ConvertMultiXSpaceToCombinedOpStatsWithCache: Finished reading cache file.
I0000 00:00:1773433312.645119 4143 multi_xplanes_to_op_stats.cc:149] ConvertMultiXSpaceToCombinedOpStatsWithCache: Overall Finished in 122.509us
I0000 00:00:1773433312.645177 4143 xplane_to_tools_data_with_profile_processor.cc:170] Total time for tool kernel_stats: 189.823us session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_tulxb1/plugins/profile/2026_03_13_20_21_52
I0000 00:00:1773433312.777128 4143 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_tulxb1/plugins/profile/2026_03_13_20_21_52
I0000 00:00:1773433312.777158 4143 xplane_to_tools_data_with_profile_processor.cc:165] Using local processing for tool: framework_op_stats
I0000 00:00:1773433312.777162 4143 multi_xplanes_to_op_stats.cc:118] ConvertMultiXSpaceToCombinedOpStatsWithCache: Started
I0000 00:00:1773433312.777222 4143 multi_xplanes_to_op_stats.cc:126] ConvertMultiXSpaceToCombinedOpStatsWithCache: Cache hit, reading binary proto
I0000 00:00:1773433312.777272 4143 multi_xplanes_to_op_stats.cc:131] ConvertMultiXSpaceToCombinedOpStatsWithCache: Finished reading cache file.
I0000 00:00:1773433312.777276 4143 multi_xplanes_to_op_stats.cc:149] ConvertMultiXSpaceToCombinedOpStatsWithCache: Overall Finished in 113.862us
I0000 00:00:1773433312.777408 4143 xplane_to_tools_data_with_profile_processor.cc:170] Total time for tool framework_op_stats: 253.442us session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_tulxb1/plugins/profile/2026_03_13_20_21_52
╔================================================================================╗
║ SUMMARY ║
╚================================================================================╝
AggregateProfilingResult(
runtime = 0.00006938s,
compile_time = 0.12139655s, # 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}:
9.2039 -22.417
20.4223 -12.6139
-13.6102 -4.97859
8.70096 12.7834
-3.66423 -14.2185
4.59465 10.6098
-2.26824 12.5408
-12.041 12.6127
4.95346 3.13896
20.1539 -3.73828Running 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.
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.