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_CxwE1j
└ @ 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 00:00:1782246235.109687 4286 profiler_session.cc:119] Profiler session initializing.
I0000 00:00:1782246235.109747 4286 profiler_session.cc:134] Profiler session started.
I0000 00:00:1782246235.110086 4286 profiler_session.cc:82] Profiler session collecting data.
I0000 00:00:1782246235.110724 4286 save_profile.cc:150] Collecting XSpace to repository: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_CxwE1j/plugins/profile/2026_06_23_20_23_55/runnervm7b5n9.xplane.pb
I0000 00:00:1782246235.110898 4286 save_profile.cc:123] Creating directory: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_CxwE1j/plugins/profile/2026_06_23_20_23_55
I0000 00:00:1782246235.111012 4286 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_CxwE1j/plugins/profile/2026_06_23_20_23_55/runnervm7b5n9.trace.json.gz
I0000 00:00:1782246235.111028 4286 profiler_session.cc:152] 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 0.0.0.0:34303
└ @ Reactant.Profiler ~/work/Reactant.jl/Reactant.jl/src/Profiler.jl:397
I0000 00:00:1782246235.127902 4286 stub_factory.cc:163] Created gRPC channel for address: 0.0.0.0:34303
┌ Debug: Starting XProf gRPC server on port 34303
└ @ Reactant.Profiler ~/work/Reactant.jl/Reactant.jl/src/Profiler.jl:413
I0000 00:00:1782246235.128373 4286 grpc_server.cc:94] Server listening on 0.0.0.0:34303 with max_concurrent_requests 1
I0000 00:00:1782246235.138288 4286 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_CxwE1j/plugins/profile/2026_06_23_20_23_55
I0000 00:00:1782246235.138307 4286 xplane_to_tools_data_with_profile_processor.cc:165] Using local processing for tool: memory_profile
I0000 00:00:1782246235.138310 4286 memory_profile_processor.cc:47] Processing memory profile for host: runnervm7b5n9
I0000 00:00:1782246235.138651 4286 xplane_to_tools_data_with_profile_processor.cc:170] Total time for tool memory_profile: 350.497us session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_CxwE1j/plugins/profile/2026_06_23_20_23_55
I0000 00:00:1782246235.152360 4286 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_CxwE1j/plugins/profile/2026_06_23_20_23_55
I0000 00:00:1782246235.152376 4286 xplane_to_tools_data_with_profile_processor.cc:165] Using local processing for tool: op_profile
I0000 00:00:1782246235.152380 4286 multi_xplanes_to_op_stats.cc:118] ConvertMultiXSpaceToCombinedOpStatsWithCache: Started
I0000 00:00:1782246235.152438 4286 multi_xplanes_to_op_stats.cc:134] ConvertMultiXSpaceToCombinedOpStatsWithCache: Cache miss, calling ConvertMultiXSpacesToCombinedOpStats
I0000 00:00:1782246235.152441 4286 multi_xplanes_to_op_stats.cc:45] ConvertMultiXSpacesToCombinedOpStats: Started. Number of XSpaces: 1
I0000 00:00:1782246235.152445 4286 multi_xplanes_to_op_stats.cc:55] ConvertMultiXSpacesToCombinedOpStats: Starting to process XSpace 0/1
I0000 00:00:1782246235.152569 4286 derived_timeline.cc:693] GenerateDerivedTimeLines: creating derived_timeline_trace_events XprofThreadPoolExecutor
I0000 00:00:1782246235.152578 4286 xprof_thread_pool_executor.cc:22] Creating derived_timeline_trace_events XprofThreadPoolExecutor with 4 threads.
I0000 00:00:1782246235.152817 4286 derived_timeline.cc:705] GenerateDerivedTimeLines: waiting for derived_timeline_trace_events threads to join
I0000 00:00:1782246235.153088 4286 derived_timeline.cc:709] GenerateDerivedTimeLines: derived_timeline_trace_events threads joined successfully
I0000 00:00:1782246235.153422 4286 derived_timeline.cc:758] GenerateDerivedTimeLines: creating ProcessTensorCorePlanes XprofThreadPoolExecutor
I0000 00:00:1782246235.153435 4286 xprof_thread_pool_executor.cc:22] Creating ProcessTensorCorePlanes XprofThreadPoolExecutor with 4 threads.
I0000 00:00:1782246235.153572 4286 derived_timeline.cc:769] GenerateDerivedTimeLines: waiting for ProcessTensorCorePlanes threads to join
I0000 00:00:1782246235.153886 4286 derived_timeline.cc:772] GenerateDerivedTimeLines: ProcessTensorCorePlanes threads joined successfully
I0000 00:00:1782246235.156211 4286 xplane_to_op_stats.cc:405] ConvertXSpaceToOpStats: creating op_stats_threads XprofThreadPoolExecutor
I0000 00:00:1782246235.156229 4286 xprof_thread_pool_executor.cc:22] Creating op_stats_threads XprofThreadPoolExecutor with 4 threads.
I0000 00:00:1782246235.156378 4286 xplane_to_op_stats.cc:461] ConvertXSpaceToOpStats: Scheduled 0 OpMetricsDb generation tasks.
I0000 00:00:1782246235.156635 4286 xplane_to_op_stats.cc:417] ConvertXSpaceToOpStats: Combining 0 op_metrics_dbs.
I0000 00:00:1782246235.156641 4286 xplane_to_op_stats.cc:422] ConvertXSpaceToOpStats: Finished combining op_metrics_dbs.
I0000 00:00:1782246235.156897 4286 xplane_to_op_stats.cc:687] ConvertXSpaceToOpStats: Final OpStats size: 222 bytes (0.000211716 MiB).
I0000 00:00:1782246235.156967 4286 multi_xplanes_to_op_stats.cc:67] ConvertMultiXSpacesToCombinedOpStats: Finished processing XSpace 0.
I0000 00:00:1782246235.156981 4286 multi_xplanes_to_op_stats.cc:72] ConvertMultiXSpacesToCombinedOpStats: Finished extracting all 1 OpStats. Time: 4.542545ms
I0000 00:00:1782246235.156989 4286 multi_xplanes_to_op_stats.cc:85] ConvertMultiXSpacesToCombinedOpStats: Starting ComputeStepIntersectionToMergeOpStats.
I0000 00:00:1782246235.156992 4286 multi_xplanes_to_op_stats.cc:94] ConvertMultiXSpacesToCombinedOpStats: Finished ComputeStepIntersectionToMergeOpStats in 1.693us
I0000 00:00:1782246235.156994 4286 multi_xplanes_to_op_stats.cc:99] ConvertMultiXSpacesToCombinedOpStats: Starting CombineAllOpStats.
I0000 00:00:1782246235.156998 4286 multi_xplanes_to_op_stats.cc:106] ConvertMultiXSpacesToCombinedOpStats: Finished CombineAllOpStats in 2.564us
I0000 00:00:1782246235.157000 4286 multi_xplanes_to_op_stats.cc:109] ConvertMultiXSpacesToCombinedOpStats: Overall Finished in 4.559831ms
I0000 00:00:1782246235.157003 4286 multi_xplanes_to_op_stats.cc:138] ConvertMultiXSpaceToCombinedOpStatsWithCache: Starting to write cache file.
I0000 00:00:1782246235.157095 4286 multi_xplanes_to_op_stats.cc:145] ConvertMultiXSpaceToCombinedOpStatsWithCache: Finished writing cache file.
I0000 00:00:1782246235.157098 4286 multi_xplanes_to_op_stats.cc:149] ConvertMultiXSpaceToCombinedOpStatsWithCache: Overall Finished in 4.717729ms
I0000 00:00:1782246235.157207 4286 xplane_to_tools_data_with_profile_processor.cc:170] Total time for tool op_profile: 4.835406ms session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_CxwE1j/plugins/profile/2026_06_23_20_23_55
┌ 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:816
I0000 00:00:1782246235.426064 4286 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_CxwE1j/plugins/profile/2026_06_23_20_23_55
I0000 00:00:1782246235.426090 4286 xplane_to_tools_data_with_profile_processor.cc:165] Using local processing for tool: overview_page
I0000 00:00:1782246235.426093 4286 overview_page_processor.cc:84] OverviewPageProcessor::ProcessSession: Started
I0000 00:00:1782246235.426096 4286 overview_page_processor.cc:86] OverviewPageProcessor::ProcessSession: Starting ConvertMultiXSpaceToCombinedOpStatsWithCache
I0000 00:00:1782246235.426098 4286 multi_xplanes_to_op_stats.cc:118] ConvertMultiXSpaceToCombinedOpStatsWithCache: Started
I0000 00:00:1782246235.426166 4286 multi_xplanes_to_op_stats.cc:126] ConvertMultiXSpaceToCombinedOpStatsWithCache: Cache hit, reading binary proto
I0000 00:00:1782246235.426221 4286 multi_xplanes_to_op_stats.cc:131] ConvertMultiXSpaceToCombinedOpStatsWithCache: Finished reading cache file.
I0000 00:00:1782246235.426223 4286 multi_xplanes_to_op_stats.cc:149] ConvertMultiXSpaceToCombinedOpStatsWithCache: Overall Finished in 125.669us
I0000 00:00:1782246235.426228 4286 overview_page_processor.cc:90] OverviewPageProcessor::ProcessSession: Starting ConvertOpStatsToOverviewPage
I0000 00:00:1782246235.426230 4286 op_stats_to_overview_page.cc:388] ConvertOpStatsToOverviewPage: Starting ComputeRunEnvironment
I0000 00:00:1782246235.426245 4286 op_stats_to_overview_page.cc:393] ConvertOpStatsToOverviewPage: Starting ComputeAnalysisResult
I0000 00:00:1782246235.426250 4286 op_stats_to_overview_page.cc:396] ConvertOpStatsToOverviewPage: Starting ConvertOpStatsToInputPipelineAnalysis
I0000 00:00:1782246235.426424 4286 op_stats_to_overview_page.cc:401] ConvertOpStatsToOverviewPage: Starting ComputeBottleneckAnalysis
I0000 00:00:1782246235.426430 4286 op_stats_to_overview_page.cc:407] ConvertOpStatsToOverviewPage: Starting ComputeGenericRecommendation
I0000 00:00:1782246235.426536 4286 op_stats_to_overview_page.cc:412] ConvertOpStatsToOverviewPage: Starting SetCommonRecommendation
I0000 00:00:1782246235.426547 4286 op_stats_to_overview_page.cc:425] ConvertOpStatsToOverviewPage: Starting PopulateOverviewDiagnostics
I0000 00:00:1782246235.426549 4286 op_stats_to_overview_page.cc:429] ConvertOpStatsToOverviewPage: Starting setting utilizations
I0000 00:00:1782246235.426551 4286 op_stats_to_overview_page.cc:435] ConvertOpStatsToOverviewPage: Overall Finished in 321.233us
I0000 00:00:1782246235.426553 4286 overview_page_processor.cc:94] OverviewPageProcessor::ProcessSession: Not a training run, Starting to convert inference stats.
I0000 00:00:1782246235.426562 4286 xprof_thread_pool_executor.cc:22] Creating ConvertMultiXSpaceToInferenceStats XprofThreadPoolExecutor with 1 threads.
I0000 00:00:1782246235.426984 4286 overview_page_processor.cc:99] OverviewPageProcessor::ProcessSession: Starting to compute InferenceLatency
I0000 00:00:1782246235.426989 4286 overview_page_processor.cc:104] OverviewPageProcessor::ProcessSession: Starting to serialize OverviewPage toJson
I0000 00:00:1782246235.427228 4286 overview_page_processor.cc:107] OverviewPageProcessor::ProcessSession: Starting to set Output
I0000 00:00:1782246235.427236 4286 overview_page_processor.cc:109] OverviewPageProcessor::ProcessSession: Overall Finished in 1.143049ms
I0000 00:00:1782246235.427248 4286 xplane_to_tools_data_with_profile_processor.cc:170] Total time for tool overview_page: 1.16394ms session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_CxwE1j/plugins/profile/2026_06_23_20_23_55
runtime: 0.00026985s
compile time: 3.86319483sjulia
Reactant.@timed nrepeat=100 linear(x, W, b)AggregateProfilingResult(
runtime = 0.00001979s,
compile_time = 0.12489665s, )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_dkiE2f
└ @ Reactant.Profiler ~/work/Reactant.jl/Reactant.jl/src/Profiler.jl:626
I0000 00:00:1782246236.135662 4286 profiler_session.cc:119] Profiler session initializing.
I0000 00:00:1782246236.135811 4286 profiler_session.cc:134] Profiler session started.
I0000 00:00:1782246236.135916 4286 profiler_session.cc:82] Profiler session collecting data.
I0000 00:00:1782246236.136397 4286 save_profile.cc:150] Collecting XSpace to repository: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_dkiE2f/plugins/profile/2026_06_23_20_23_56/runnervm7b5n9.xplane.pb
I0000 00:00:1782246236.136546 4286 save_profile.cc:123] Creating directory: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_dkiE2f/plugins/profile/2026_06_23_20_23_56
I0000 00:00:1782246236.136654 4286 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_dkiE2f/plugins/profile/2026_06_23_20_23_56/runnervm7b5n9.trace.json.gz
I0000 00:00:1782246236.136668 4286 profiler_session.cc:152] Profiler session tear down.
I0000 00:00:1782246236.136729 4286 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_dkiE2f/plugins/profile/2026_06_23_20_23_56
I0000 00:00:1782246236.136735 4286 xplane_to_tools_data_with_profile_processor.cc:165] Using local processing for tool: memory_profile
I0000 00:00:1782246236.136738 4286 memory_profile_processor.cc:47] Processing memory profile for host: runnervm7b5n9
I0000 00:00:1782246236.136915 4286 xplane_to_tools_data_with_profile_processor.cc:170] Total time for tool memory_profile: 185.189us session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_dkiE2f/plugins/profile/2026_06_23_20_23_56
I0000 00:00:1782246236.136941 4286 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_dkiE2f/plugins/profile/2026_06_23_20_23_56
I0000 00:00:1782246236.136944 4286 xplane_to_tools_data_with_profile_processor.cc:165] Using local processing for tool: op_profile
I0000 00:00:1782246236.136947 4286 multi_xplanes_to_op_stats.cc:118] ConvertMultiXSpaceToCombinedOpStatsWithCache: Started
I0000 00:00:1782246236.136977 4286 multi_xplanes_to_op_stats.cc:134] ConvertMultiXSpaceToCombinedOpStatsWithCache: Cache miss, calling ConvertMultiXSpacesToCombinedOpStats
I0000 00:00:1782246236.136980 4286 multi_xplanes_to_op_stats.cc:45] ConvertMultiXSpacesToCombinedOpStats: Started. Number of XSpaces: 1
I0000 00:00:1782246236.136983 4286 multi_xplanes_to_op_stats.cc:55] ConvertMultiXSpacesToCombinedOpStats: Starting to process XSpace 0/1
I0000 00:00:1782246236.137051 4286 derived_timeline.cc:693] GenerateDerivedTimeLines: creating derived_timeline_trace_events XprofThreadPoolExecutor
I0000 00:00:1782246236.137059 4286 xprof_thread_pool_executor.cc:22] Creating derived_timeline_trace_events XprofThreadPoolExecutor with 4 threads.
I0000 00:00:1782246236.137237 4286 derived_timeline.cc:705] GenerateDerivedTimeLines: waiting for derived_timeline_trace_events threads to join
I0000 00:00:1782246236.137509 4286 derived_timeline.cc:709] GenerateDerivedTimeLines: derived_timeline_trace_events threads joined successfully
I0000 00:00:1782246236.137951 4286 derived_timeline.cc:758] GenerateDerivedTimeLines: creating ProcessTensorCorePlanes XprofThreadPoolExecutor
I0000 00:00:1782246236.137972 4286 xprof_thread_pool_executor.cc:22] Creating ProcessTensorCorePlanes XprofThreadPoolExecutor with 4 threads.
I0000 00:00:1782246236.138113 4286 derived_timeline.cc:769] GenerateDerivedTimeLines: waiting for ProcessTensorCorePlanes threads to join
I0000 00:00:1782246236.138349 4286 derived_timeline.cc:772] GenerateDerivedTimeLines: ProcessTensorCorePlanes threads joined successfully
I0000 00:00:1782246236.138796 4286 xplane_to_op_stats.cc:405] ConvertXSpaceToOpStats: creating op_stats_threads XprofThreadPoolExecutor
I0000 00:00:1782246236.138821 4286 xprof_thread_pool_executor.cc:22] Creating op_stats_threads XprofThreadPoolExecutor with 4 threads.
I0000 00:00:1782246236.138955 4286 xplane_to_op_stats.cc:461] ConvertXSpaceToOpStats: Scheduled 0 OpMetricsDb generation tasks.
I0000 00:00:1782246236.139193 4286 xplane_to_op_stats.cc:417] ConvertXSpaceToOpStats: Combining 0 op_metrics_dbs.
I0000 00:00:1782246236.139204 4286 xplane_to_op_stats.cc:422] ConvertXSpaceToOpStats: Finished combining op_metrics_dbs.
I0000 00:00:1782246236.139390 4286 xplane_to_op_stats.cc:687] ConvertXSpaceToOpStats: Final OpStats size: 265 bytes (0.000252724 MiB).
I0000 00:00:1782246236.139471 4286 multi_xplanes_to_op_stats.cc:67] ConvertMultiXSpacesToCombinedOpStats: Finished processing XSpace 0.
I0000 00:00:1782246236.139500 4286 multi_xplanes_to_op_stats.cc:72] ConvertMultiXSpacesToCombinedOpStats: Finished extracting all 1 OpStats. Time: 2.523074ms
I0000 00:00:1782246236.139506 4286 multi_xplanes_to_op_stats.cc:85] ConvertMultiXSpacesToCombinedOpStats: Starting ComputeStepIntersectionToMergeOpStats.
I0000 00:00:1782246236.139509 4286 multi_xplanes_to_op_stats.cc:94] ConvertMultiXSpacesToCombinedOpStats: Finished ComputeStepIntersectionToMergeOpStats in 1.813us
I0000 00:00:1782246236.139511 4286 multi_xplanes_to_op_stats.cc:99] ConvertMultiXSpacesToCombinedOpStats: Starting CombineAllOpStats.
I0000 00:00:1782246236.139515 4286 multi_xplanes_to_op_stats.cc:106] ConvertMultiXSpacesToCombinedOpStats: Finished CombineAllOpStats in 3.215us
I0000 00:00:1782246236.139517 4286 multi_xplanes_to_op_stats.cc:109] ConvertMultiXSpacesToCombinedOpStats: Overall Finished in 2.538087ms
I0000 00:00:1782246236.139521 4286 multi_xplanes_to_op_stats.cc:138] ConvertMultiXSpaceToCombinedOpStatsWithCache: Starting to write cache file.
I0000 00:00:1782246236.139579 4286 multi_xplanes_to_op_stats.cc:145] ConvertMultiXSpaceToCombinedOpStatsWithCache: Finished writing cache file.
I0000 00:00:1782246236.139582 4286 multi_xplanes_to_op_stats.cc:149] ConvertMultiXSpaceToCombinedOpStatsWithCache: Overall Finished in 2.635443ms
I0000 00:00:1782246236.139604 4286 xplane_to_tools_data_with_profile_processor.cc:170] Total time for tool op_profile: 2.662094ms session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_dkiE2f/plugins/profile/2026_06_23_20_23_56
┌ 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:816
I0000 00:00:1782246236.139978 4286 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_dkiE2f/plugins/profile/2026_06_23_20_23_56
I0000 00:00:1782246236.139987 4286 xplane_to_tools_data_with_profile_processor.cc:165] Using local processing for tool: overview_page
I0000 00:00:1782246236.139989 4286 overview_page_processor.cc:84] OverviewPageProcessor::ProcessSession: Started
I0000 00:00:1782246236.139991 4286 overview_page_processor.cc:86] OverviewPageProcessor::ProcessSession: Starting ConvertMultiXSpaceToCombinedOpStatsWithCache
I0000 00:00:1782246236.139993 4286 multi_xplanes_to_op_stats.cc:118] ConvertMultiXSpaceToCombinedOpStatsWithCache: Started
I0000 00:00:1782246236.140031 4286 multi_xplanes_to_op_stats.cc:126] ConvertMultiXSpaceToCombinedOpStatsWithCache: Cache hit, reading binary proto
I0000 00:00:1782246236.140068 4286 multi_xplanes_to_op_stats.cc:131] ConvertMultiXSpaceToCombinedOpStatsWithCache: Finished reading cache file.
I0000 00:00:1782246236.140070 4286 multi_xplanes_to_op_stats.cc:149] ConvertMultiXSpaceToCombinedOpStatsWithCache: Overall Finished in 77.086us
I0000 00:00:1782246236.140072 4286 overview_page_processor.cc:90] OverviewPageProcessor::ProcessSession: Starting ConvertOpStatsToOverviewPage
I0000 00:00:1782246236.140075 4286 op_stats_to_overview_page.cc:388] ConvertOpStatsToOverviewPage: Starting ComputeRunEnvironment
I0000 00:00:1782246236.140079 4286 op_stats_to_overview_page.cc:393] ConvertOpStatsToOverviewPage: Starting ComputeAnalysisResult
I0000 00:00:1782246236.140083 4286 op_stats_to_overview_page.cc:396] ConvertOpStatsToOverviewPage: Starting ConvertOpStatsToInputPipelineAnalysis
I0000 00:00:1782246236.140116 4286 op_stats_to_overview_page.cc:401] ConvertOpStatsToOverviewPage: Starting ComputeBottleneckAnalysis
I0000 00:00:1782246236.140120 4286 op_stats_to_overview_page.cc:407] ConvertOpStatsToOverviewPage: Starting ComputeGenericRecommendation
I0000 00:00:1782246236.140125 4286 op_stats_to_overview_page.cc:412] ConvertOpStatsToOverviewPage: Starting SetCommonRecommendation
I0000 00:00:1782246236.140131 4286 op_stats_to_overview_page.cc:425] ConvertOpStatsToOverviewPage: Starting PopulateOverviewDiagnostics
I0000 00:00:1782246236.140133 4286 op_stats_to_overview_page.cc:429] ConvertOpStatsToOverviewPage: Starting setting utilizations
I0000 00:00:1782246236.140135 4286 op_stats_to_overview_page.cc:435] ConvertOpStatsToOverviewPage: Overall Finished in 61.001us
I0000 00:00:1782246236.140137 4286 overview_page_processor.cc:94] OverviewPageProcessor::ProcessSession: Not a training run, Starting to convert inference stats.
I0000 00:00:1782246236.140142 4286 xprof_thread_pool_executor.cc:22] Creating ConvertMultiXSpaceToInferenceStats XprofThreadPoolExecutor with 1 threads.
I0000 00:00:1782246236.140405 4286 overview_page_processor.cc:99] OverviewPageProcessor::ProcessSession: Starting to compute InferenceLatency
I0000 00:00:1782246236.140411 4286 overview_page_processor.cc:104] OverviewPageProcessor::ProcessSession: Starting to serialize OverviewPage toJson
I0000 00:00:1782246236.140612 4286 overview_page_processor.cc:107] OverviewPageProcessor::ProcessSession: Starting to set Output
I0000 00:00:1782246236.140620 4286 overview_page_processor.cc:109] OverviewPageProcessor::ProcessSession: Overall Finished in 631.38us
I0000 00:00:1782246236.140630 4286 xplane_to_tools_data_with_profile_processor.cc:170] Total time for tool overview_page: 647.093us session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_dkiE2f/plugins/profile/2026_06_23_20_23_56
I0000 00:00:1782246236.231877 4286 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_dkiE2f/plugins/profile/2026_06_23_20_23_56
I0000 00:00:1782246236.231910 4286 xplane_to_tools_data_with_profile_processor.cc:165] Using local processing for tool: kernel_stats
I0000 00:00:1782246236.231914 4286 multi_xplanes_to_op_stats.cc:118] ConvertMultiXSpaceToCombinedOpStatsWithCache: Started
I0000 00:00:1782246236.231981 4286 multi_xplanes_to_op_stats.cc:126] ConvertMultiXSpaceToCombinedOpStatsWithCache: Cache hit, reading binary proto
I0000 00:00:1782246236.232043 4286 multi_xplanes_to_op_stats.cc:131] ConvertMultiXSpaceToCombinedOpStatsWithCache: Finished reading cache file.
I0000 00:00:1782246236.232045 4286 multi_xplanes_to_op_stats.cc:149] ConvertMultiXSpaceToCombinedOpStatsWithCache: Overall Finished in 131.398us
I0000 00:00:1782246236.232114 4286 xplane_to_tools_data_with_profile_processor.cc:170] Total time for tool kernel_stats: 209.836us session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_dkiE2f/plugins/profile/2026_06_23_20_23_56
I0000 00:00:1782246236.358622 4286 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_dkiE2f/plugins/profile/2026_06_23_20_23_56
I0000 00:00:1782246236.358655 4286 xplane_to_tools_data_with_profile_processor.cc:165] Using local processing for tool: framework_op_stats
I0000 00:00:1782246236.358659 4286 multi_xplanes_to_op_stats.cc:118] ConvertMultiXSpaceToCombinedOpStatsWithCache: Started
I0000 00:00:1782246236.358727 4286 multi_xplanes_to_op_stats.cc:126] ConvertMultiXSpaceToCombinedOpStatsWithCache: Cache hit, reading binary proto
I0000 00:00:1782246236.358804 4286 multi_xplanes_to_op_stats.cc:131] ConvertMultiXSpaceToCombinedOpStatsWithCache: Finished reading cache file.
I0000 00:00:1782246236.358806 4286 multi_xplanes_to_op_stats.cc:149] ConvertMultiXSpaceToCombinedOpStatsWithCache: Overall Finished in 147.792us
I0000 00:00:1782246236.358957 4286 xplane_to_tools_data_with_profile_processor.cc:170] Total time for tool framework_op_stats: 304.958us session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_dkiE2f/plugins/profile/2026_06_23_20_23_56
╔================================================================================╗
║ SUMMARY ║
╚================================================================================╝
AggregateProfilingResult(
runtime = 0.00007984s,
compile_time = 0.11812132s, # 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}:
1.91194 5.01056
10.9613 20.9626
-8.88414 -10.8305
8.21949 -3.68566
2.91005 -3.84449
7.83244 3.84839
2.14763 -9.51182
0.303694 14.0142
-7.84805 5.18152
-11.639 -11.7354Running 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.