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_Y5Hful
└ @ 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 00:00:1776942011.073274 4345 profiler_session.cc:119] Profiler session initializing.
I0000 00:00:1776942011.073310 4345 profiler_session.cc:134] Profiler session started.
I0000 00:00:1776942011.073617 4345 profiler_session.cc:82] Profiler session collecting data.
I0000 00:00:1776942011.074174 4345 save_profile.cc:150] Collecting XSpace to repository: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_Y5Hful/plugins/profile/2026_04_23_11_00_11/runnervmeorf1.xplane.pb
I0000 00:00:1776942011.074320 4345 save_profile.cc:123] Creating directory: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_Y5Hful/plugins/profile/2026_04_23_11_00_11
I0000 00:00:1776942011.074432 4345 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_Y5Hful/plugins/profile/2026_04_23_11_00_11/runnervmeorf1.trace.json.gz
I0000 00:00:1776942011.074449 4345 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 0.0.0.0:45827
└ @ Reactant.Profiler ~/work/Reactant.jl/Reactant.jl/src/Profiler.jl:397
I0000 00:00:1776942011.089415 4345 stub_factory.cc:163] Created gRPC channel for address: 0.0.0.0:45827
┌ Debug: Starting XProf gRPC server on port 45827
└ @ Reactant.Profiler ~/work/Reactant.jl/Reactant.jl/src/Profiler.jl:413
I0000 00:00:1776942011.089851 4345 grpc_server.cc:94] Server listening on 0.0.0.0:45827 with max_concurrent_requests 1
I0000 00:00:1776942011.098627 4345 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_Y5Hful/plugins/profile/2026_04_23_11_00_11
I0000 00:00:1776942011.098640 4345 xplane_to_tools_data_with_profile_processor.cc:165] Using local processing for tool: memory_profile
I0000 00:00:1776942011.098644 4345 memory_profile_processor.cc:47] Processing memory profile for host: runnervmeorf1
I0000 00:00:1776942011.098920 4345 xplane_to_tools_data_with_profile_processor.cc:170] Total time for tool memory_profile: 284.819us session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_Y5Hful/plugins/profile/2026_04_23_11_00_11
I0000 00:00:1776942011.111658 4345 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_Y5Hful/plugins/profile/2026_04_23_11_00_11
I0000 00:00:1776942011.111671 4345 xplane_to_tools_data_with_profile_processor.cc:165] Using local processing for tool: op_profile
I0000 00:00:1776942011.111674 4345 multi_xplanes_to_op_stats.cc:118] ConvertMultiXSpaceToCombinedOpStatsWithCache: Started
I0000 00:00:1776942011.111718 4345 multi_xplanes_to_op_stats.cc:134] ConvertMultiXSpaceToCombinedOpStatsWithCache: Cache miss, calling ConvertMultiXSpacesToCombinedOpStats
I0000 00:00:1776942011.111720 4345 multi_xplanes_to_op_stats.cc:45] ConvertMultiXSpacesToCombinedOpStats: Started. Number of XSpaces: 1
I0000 00:00:1776942011.111724 4345 multi_xplanes_to_op_stats.cc:55] ConvertMultiXSpacesToCombinedOpStats: Starting to process XSpace 0/1
I0000 00:00:1776942011.111835 4345 derived_timeline.cc:693] GenerateDerivedTimeLines: creating derived_timeline_trace_events XprofThreadPoolExecutor
I0000 00:00:1776942011.111844 4345 xprof_thread_pool_executor.cc:22] Creating derived_timeline_trace_events XprofThreadPoolExecutor with 4 threads.
I0000 00:00:1776942011.112096 4345 derived_timeline.cc:705] GenerateDerivedTimeLines: waiting for derived_timeline_trace_events threads to join
I0000 00:00:1776942011.112387 4345 derived_timeline.cc:709] GenerateDerivedTimeLines: derived_timeline_trace_events threads joined successfully
I0000 00:00:1776942011.112649 4345 derived_timeline.cc:758] GenerateDerivedTimeLines: creating ProcessTensorCorePlanes XprofThreadPoolExecutor
I0000 00:00:1776942011.112659 4345 xprof_thread_pool_executor.cc:22] Creating ProcessTensorCorePlanes XprofThreadPoolExecutor with 4 threads.
I0000 00:00:1776942011.112795 4345 derived_timeline.cc:769] GenerateDerivedTimeLines: waiting for ProcessTensorCorePlanes threads to join
I0000 00:00:1776942011.113091 4345 derived_timeline.cc:772] GenerateDerivedTimeLines: ProcessTensorCorePlanes threads joined successfully
I0000 00:00:1776942011.115663 4345 xplane_to_op_stats.cc:405] ConvertXSpaceToOpStats: creating op_stats_threads XprofThreadPoolExecutor
I0000 00:00:1776942011.115676 4345 xprof_thread_pool_executor.cc:22] Creating op_stats_threads XprofThreadPoolExecutor with 4 threads.
I0000 00:00:1776942011.115817 4345 xplane_to_op_stats.cc:461] ConvertXSpaceToOpStats: Scheduled 0 OpMetricsDb generation tasks.
I0000 00:00:1776942011.116290 4345 xplane_to_op_stats.cc:417] ConvertXSpaceToOpStats: Combining 0 op_metrics_dbs.
I0000 00:00:1776942011.116299 4345 xplane_to_op_stats.cc:422] ConvertXSpaceToOpStats: Finished combining op_metrics_dbs.
I0000 00:00:1776942011.116502 4345 xplane_to_op_stats.cc:687] ConvertXSpaceToOpStats: Final OpStats size: 220 bytes (0.000209808 MiB).
I0000 00:00:1776942011.116568 4345 multi_xplanes_to_op_stats.cc:67] ConvertMultiXSpacesToCombinedOpStats: Finished processing XSpace 0.
I0000 00:00:1776942011.116580 4345 multi_xplanes_to_op_stats.cc:72] ConvertMultiXSpacesToCombinedOpStats: Finished extracting all 1 OpStats. Time: 4.861658ms
I0000 00:00:1776942011.116587 4345 multi_xplanes_to_op_stats.cc:85] ConvertMultiXSpacesToCombinedOpStats: Starting ComputeStepIntersectionToMergeOpStats.
I0000 00:00:1776942011.116590 4345 multi_xplanes_to_op_stats.cc:94] ConvertMultiXSpacesToCombinedOpStats: Finished ComputeStepIntersectionToMergeOpStats in 1.453us
I0000 00:00:1776942011.116592 4345 multi_xplanes_to_op_stats.cc:99] ConvertMultiXSpacesToCombinedOpStats: Starting CombineAllOpStats.
I0000 00:00:1776942011.116596 4345 multi_xplanes_to_op_stats.cc:106] ConvertMultiXSpacesToCombinedOpStats: Finished CombineAllOpStats in 2.975us
I0000 00:00:1776942011.116598 4345 multi_xplanes_to_op_stats.cc:109] ConvertMultiXSpacesToCombinedOpStats: Overall Finished in 4.878239ms
I0000 00:00:1776942011.116601 4345 multi_xplanes_to_op_stats.cc:138] ConvertMultiXSpaceToCombinedOpStatsWithCache: Starting to write cache file.
I0000 00:00:1776942011.116679 4345 multi_xplanes_to_op_stats.cc:145] ConvertMultiXSpaceToCombinedOpStatsWithCache: Finished writing cache file.
I0000 00:00:1776942011.116683 4345 multi_xplanes_to_op_stats.cc:149] ConvertMultiXSpaceToCombinedOpStatsWithCache: Overall Finished in 5.008921ms
I0000 00:00:1776942011.116786 4345 xplane_to_tools_data_with_profile_processor.cc:170] Total time for tool op_profile: 5.119456ms session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_Y5Hful/plugins/profile/2026_04_23_11_00_11
┌ 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 00:00:1776942011.378994 4345 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_Y5Hful/plugins/profile/2026_04_23_11_00_11
I0000 00:00:1776942011.379018 4345 xplane_to_tools_data_with_profile_processor.cc:165] Using local processing for tool: overview_page
I0000 00:00:1776942011.379021 4345 overview_page_processor.cc:84] OverviewPageProcessor::ProcessSession: Started
I0000 00:00:1776942011.379024 4345 overview_page_processor.cc:86] OverviewPageProcessor::ProcessSession: Starting ConvertMultiXSpaceToCombinedOpStatsWithCache
I0000 00:00:1776942011.379026 4345 multi_xplanes_to_op_stats.cc:118] ConvertMultiXSpaceToCombinedOpStatsWithCache: Started
I0000 00:00:1776942011.379087 4345 multi_xplanes_to_op_stats.cc:126] ConvertMultiXSpaceToCombinedOpStatsWithCache: Cache hit, reading binary proto
I0000 00:00:1776942011.379139 4345 multi_xplanes_to_op_stats.cc:131] ConvertMultiXSpaceToCombinedOpStatsWithCache: Finished reading cache file.
I0000 00:00:1776942011.379141 4345 multi_xplanes_to_op_stats.cc:149] ConvertMultiXSpaceToCombinedOpStatsWithCache: Overall Finished in 115.986us
I0000 00:00:1776942011.379146 4345 overview_page_processor.cc:90] OverviewPageProcessor::ProcessSession: Starting ConvertOpStatsToOverviewPage
I0000 00:00:1776942011.379154 4345 op_stats_to_overview_page.cc:388] ConvertOpStatsToOverviewPage: Starting ComputeRunEnvironment
I0000 00:00:1776942011.379161 4345 op_stats_to_overview_page.cc:393] ConvertOpStatsToOverviewPage: Starting ComputeAnalysisResult
I0000 00:00:1776942011.379166 4345 op_stats_to_overview_page.cc:396] ConvertOpStatsToOverviewPage: Starting ConvertOpStatsToInputPipelineAnalysis
I0000 00:00:1776942011.379333 4345 op_stats_to_overview_page.cc:401] ConvertOpStatsToOverviewPage: Starting ComputeBottleneckAnalysis
I0000 00:00:1776942011.379340 4345 op_stats_to_overview_page.cc:407] ConvertOpStatsToOverviewPage: Starting ComputeGenericRecommendation
I0000 00:00:1776942011.379442 4345 op_stats_to_overview_page.cc:412] ConvertOpStatsToOverviewPage: Starting SetCommonRecommendation
I0000 00:00:1776942011.379452 4345 op_stats_to_overview_page.cc:425] ConvertOpStatsToOverviewPage: Starting PopulateOverviewDiagnostics
I0000 00:00:1776942011.379454 4345 op_stats_to_overview_page.cc:429] ConvertOpStatsToOverviewPage: Starting setting utilizations
I0000 00:00:1776942011.379456 4345 op_stats_to_overview_page.cc:435] ConvertOpStatsToOverviewPage: Overall Finished in 301.81us
I0000 00:00:1776942011.379458 4345 overview_page_processor.cc:94] OverviewPageProcessor::ProcessSession: Not a training run, Starting to convert inference stats.
I0000 00:00:1776942011.379466 4345 xprof_thread_pool_executor.cc:22] Creating ConvertMultiXSpaceToInferenceStats XprofThreadPoolExecutor with 1 threads.
I0000 00:00:1776942011.379872 4345 overview_page_processor.cc:99] OverviewPageProcessor::ProcessSession: Starting to compute InferenceLatency
I0000 00:00:1776942011.379880 4345 overview_page_processor.cc:104] OverviewPageProcessor::ProcessSession: Starting to serialize OverviewPage toJson
I0000 00:00:1776942011.380130 4345 overview_page_processor.cc:107] OverviewPageProcessor::ProcessSession: Starting to set Output
I0000 00:00:1776942011.380140 4345 overview_page_processor.cc:109] OverviewPageProcessor::ProcessSession: Overall Finished in 1.119307ms
I0000 00:00:1776942011.380152 4345 xplane_to_tools_data_with_profile_processor.cc:170] Total time for tool overview_page: 1.139995ms session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_Y5Hful/plugins/profile/2026_04_23_11_00_11
runtime: 0.00025809s
compile time: 4.00847845sjulia
Reactant.@timed nrepeat=100 linear(x, W, b)AggregateProfilingResult(
runtime = 0.00003117s,
compile_time = 0.11826258s, )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_uh4FCm
└ @ Reactant.Profiler ~/work/Reactant.jl/Reactant.jl/src/Profiler.jl:626
I0000 00:00:1776942012.070384 4345 profiler_session.cc:119] Profiler session initializing.
I0000 00:00:1776942012.070469 4345 profiler_session.cc:134] Profiler session started.
I0000 00:00:1776942012.070564 4345 profiler_session.cc:82] Profiler session collecting data.
I0000 00:00:1776942012.071011 4345 save_profile.cc:150] Collecting XSpace to repository: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_uh4FCm/plugins/profile/2026_04_23_11_00_12/runnervmeorf1.xplane.pb
I0000 00:00:1776942012.071161 4345 save_profile.cc:123] Creating directory: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_uh4FCm/plugins/profile/2026_04_23_11_00_12
I0000 00:00:1776942012.071280 4345 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_uh4FCm/plugins/profile/2026_04_23_11_00_12/runnervmeorf1.trace.json.gz
I0000 00:00:1776942012.071296 4345 profiler_session.cc:152] Profiler session tear down.
I0000 00:00:1776942012.071350 4345 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_uh4FCm/plugins/profile/2026_04_23_11_00_12
I0000 00:00:1776942012.071356 4345 xplane_to_tools_data_with_profile_processor.cc:165] Using local processing for tool: memory_profile
I0000 00:00:1776942012.071358 4345 memory_profile_processor.cc:47] Processing memory profile for host: runnervmeorf1
I0000 00:00:1776942012.071500 4345 xplane_to_tools_data_with_profile_processor.cc:170] Total time for tool memory_profile: 150.46us session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_uh4FCm/plugins/profile/2026_04_23_11_00_12
I0000 00:00:1776942012.071526 4345 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_uh4FCm/plugins/profile/2026_04_23_11_00_12
I0000 00:00:1776942012.071530 4345 xplane_to_tools_data_with_profile_processor.cc:165] Using local processing for tool: op_profile
I0000 00:00:1776942012.071532 4345 multi_xplanes_to_op_stats.cc:118] ConvertMultiXSpaceToCombinedOpStatsWithCache: Started
I0000 00:00:1776942012.071560 4345 multi_xplanes_to_op_stats.cc:134] ConvertMultiXSpaceToCombinedOpStatsWithCache: Cache miss, calling ConvertMultiXSpacesToCombinedOpStats
I0000 00:00:1776942012.071562 4345 multi_xplanes_to_op_stats.cc:45] ConvertMultiXSpacesToCombinedOpStats: Started. Number of XSpaces: 1
I0000 00:00:1776942012.071566 4345 multi_xplanes_to_op_stats.cc:55] ConvertMultiXSpacesToCombinedOpStats: Starting to process XSpace 0/1
I0000 00:00:1776942012.071637 4345 derived_timeline.cc:693] GenerateDerivedTimeLines: creating derived_timeline_trace_events XprofThreadPoolExecutor
I0000 00:00:1776942012.071645 4345 xprof_thread_pool_executor.cc:22] Creating derived_timeline_trace_events XprofThreadPoolExecutor with 4 threads.
I0000 00:00:1776942012.071833 4345 derived_timeline.cc:705] GenerateDerivedTimeLines: waiting for derived_timeline_trace_events threads to join
I0000 00:00:1776942012.072155 4345 derived_timeline.cc:709] GenerateDerivedTimeLines: derived_timeline_trace_events threads joined successfully
I0000 00:00:1776942012.072496 4345 derived_timeline.cc:758] GenerateDerivedTimeLines: creating ProcessTensorCorePlanes XprofThreadPoolExecutor
I0000 00:00:1776942012.072514 4345 xprof_thread_pool_executor.cc:22] Creating ProcessTensorCorePlanes XprofThreadPoolExecutor with 4 threads.
I0000 00:00:1776942012.072658 4345 derived_timeline.cc:769] GenerateDerivedTimeLines: waiting for ProcessTensorCorePlanes threads to join
I0000 00:00:1776942012.072928 4345 derived_timeline.cc:772] GenerateDerivedTimeLines: ProcessTensorCorePlanes threads joined successfully
I0000 00:00:1776942012.073325 4345 xplane_to_op_stats.cc:405] ConvertXSpaceToOpStats: creating op_stats_threads XprofThreadPoolExecutor
I0000 00:00:1776942012.073344 4345 xprof_thread_pool_executor.cc:22] Creating op_stats_threads XprofThreadPoolExecutor with 4 threads.
I0000 00:00:1776942012.073479 4345 xplane_to_op_stats.cc:461] ConvertXSpaceToOpStats: Scheduled 0 OpMetricsDb generation tasks.
I0000 00:00:1776942012.073733 4345 xplane_to_op_stats.cc:417] ConvertXSpaceToOpStats: Combining 0 op_metrics_dbs.
I0000 00:00:1776942012.073742 4345 xplane_to_op_stats.cc:422] ConvertXSpaceToOpStats: Finished combining op_metrics_dbs.
I0000 00:00:1776942012.073880 4345 xplane_to_op_stats.cc:687] ConvertXSpaceToOpStats: Final OpStats size: 262 bytes (0.000249863 MiB).
I0000 00:00:1776942012.073945 4345 multi_xplanes_to_op_stats.cc:67] ConvertMultiXSpacesToCombinedOpStats: Finished processing XSpace 0.
I0000 00:00:1776942012.074017 4345 multi_xplanes_to_op_stats.cc:72] ConvertMultiXSpacesToCombinedOpStats: Finished extracting all 1 OpStats. Time: 2.45754ms
I0000 00:00:1776942012.074023 4345 multi_xplanes_to_op_stats.cc:85] ConvertMultiXSpacesToCombinedOpStats: Starting ComputeStepIntersectionToMergeOpStats.
I0000 00:00:1776942012.074026 4345 multi_xplanes_to_op_stats.cc:94] ConvertMultiXSpacesToCombinedOpStats: Finished ComputeStepIntersectionToMergeOpStats in 1.623us
I0000 00:00:1776942012.074028 4345 multi_xplanes_to_op_stats.cc:99] ConvertMultiXSpacesToCombinedOpStats: Starting CombineAllOpStats.
I0000 00:00:1776942012.074033 4345 multi_xplanes_to_op_stats.cc:106] ConvertMultiXSpacesToCombinedOpStats: Finished CombineAllOpStats in 4.438us
I0000 00:00:1776942012.074035 4345 multi_xplanes_to_op_stats.cc:109] ConvertMultiXSpacesToCombinedOpStats: Overall Finished in 2.473379ms
I0000 00:00:1776942012.074038 4345 multi_xplanes_to_op_stats.cc:138] ConvertMultiXSpaceToCombinedOpStatsWithCache: Starting to write cache file.
I0000 00:00:1776942012.074088 4345 multi_xplanes_to_op_stats.cc:145] ConvertMultiXSpaceToCombinedOpStatsWithCache: Finished writing cache file.
I0000 00:00:1776942012.074092 4345 multi_xplanes_to_op_stats.cc:149] ConvertMultiXSpaceToCombinedOpStatsWithCache: Overall Finished in 2.559589ms
I0000 00:00:1776942012.074114 4345 xplane_to_tools_data_with_profile_processor.cc:170] Total time for tool op_profile: 2.585928ms session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_uh4FCm/plugins/profile/2026_04_23_11_00_12
┌ 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 00:00:1776942012.074411 4345 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_uh4FCm/plugins/profile/2026_04_23_11_00_12
I0000 00:00:1776942012.074418 4345 xplane_to_tools_data_with_profile_processor.cc:165] Using local processing for tool: overview_page
I0000 00:00:1776942012.074420 4345 overview_page_processor.cc:84] OverviewPageProcessor::ProcessSession: Started
I0000 00:00:1776942012.074422 4345 overview_page_processor.cc:86] OverviewPageProcessor::ProcessSession: Starting ConvertMultiXSpaceToCombinedOpStatsWithCache
I0000 00:00:1776942012.074424 4345 multi_xplanes_to_op_stats.cc:118] ConvertMultiXSpaceToCombinedOpStatsWithCache: Started
I0000 00:00:1776942012.074455 4345 multi_xplanes_to_op_stats.cc:126] ConvertMultiXSpaceToCombinedOpStatsWithCache: Cache hit, reading binary proto
I0000 00:00:1776942012.074489 4345 multi_xplanes_to_op_stats.cc:131] ConvertMultiXSpaceToCombinedOpStatsWithCache: Finished reading cache file.
I0000 00:00:1776942012.074492 4345 multi_xplanes_to_op_stats.cc:149] ConvertMultiXSpaceToCombinedOpStatsWithCache: Overall Finished in 68.407us
I0000 00:00:1776942012.074494 4345 overview_page_processor.cc:90] OverviewPageProcessor::ProcessSession: Starting ConvertOpStatsToOverviewPage
I0000 00:00:1776942012.074496 4345 op_stats_to_overview_page.cc:388] ConvertOpStatsToOverviewPage: Starting ComputeRunEnvironment
I0000 00:00:1776942012.074500 4345 op_stats_to_overview_page.cc:393] ConvertOpStatsToOverviewPage: Starting ComputeAnalysisResult
I0000 00:00:1776942012.074504 4345 op_stats_to_overview_page.cc:396] ConvertOpStatsToOverviewPage: Starting ConvertOpStatsToInputPipelineAnalysis
I0000 00:00:1776942012.074532 4345 op_stats_to_overview_page.cc:401] ConvertOpStatsToOverviewPage: Starting ComputeBottleneckAnalysis
I0000 00:00:1776942012.074536 4345 op_stats_to_overview_page.cc:407] ConvertOpStatsToOverviewPage: Starting ComputeGenericRecommendation
I0000 00:00:1776942012.074541 4345 op_stats_to_overview_page.cc:412] ConvertOpStatsToOverviewPage: Starting SetCommonRecommendation
I0000 00:00:1776942012.074546 4345 op_stats_to_overview_page.cc:425] ConvertOpStatsToOverviewPage: Starting PopulateOverviewDiagnostics
I0000 00:00:1776942012.074548 4345 op_stats_to_overview_page.cc:429] ConvertOpStatsToOverviewPage: Starting setting utilizations
I0000 00:00:1776942012.074550 4345 op_stats_to_overview_page.cc:435] ConvertOpStatsToOverviewPage: Overall Finished in 53.94us
I0000 00:00:1776942012.074552 4345 overview_page_processor.cc:94] OverviewPageProcessor::ProcessSession: Not a training run, Starting to convert inference stats.
I0000 00:00:1776942012.074556 4345 xprof_thread_pool_executor.cc:22] Creating ConvertMultiXSpaceToInferenceStats XprofThreadPoolExecutor with 1 threads.
I0000 00:00:1776942012.074803 4345 overview_page_processor.cc:99] OverviewPageProcessor::ProcessSession: Starting to compute InferenceLatency
I0000 00:00:1776942012.074810 4345 overview_page_processor.cc:104] OverviewPageProcessor::ProcessSession: Starting to serialize OverviewPage toJson
I0000 00:00:1776942012.075040 4345 overview_page_processor.cc:107] OverviewPageProcessor::ProcessSession: Starting to set Output
I0000 00:00:1776942012.075051 4345 overview_page_processor.cc:109] OverviewPageProcessor::ProcessSession: Overall Finished in 630.73us
I0000 00:00:1776942012.075062 4345 xplane_to_tools_data_with_profile_processor.cc:170] Total time for tool overview_page: 646.239us session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_uh4FCm/plugins/profile/2026_04_23_11_00_12
I0000 00:00:1776942012.170435 4345 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_uh4FCm/plugins/profile/2026_04_23_11_00_12
I0000 00:00:1776942012.170462 4345 xplane_to_tools_data_with_profile_processor.cc:165] Using local processing for tool: kernel_stats
I0000 00:00:1776942012.170465 4345 multi_xplanes_to_op_stats.cc:118] ConvertMultiXSpaceToCombinedOpStatsWithCache: Started
I0000 00:00:1776942012.170521 4345 multi_xplanes_to_op_stats.cc:126] ConvertMultiXSpaceToCombinedOpStatsWithCache: Cache hit, reading binary proto
I0000 00:00:1776942012.170572 4345 multi_xplanes_to_op_stats.cc:131] ConvertMultiXSpaceToCombinedOpStatsWithCache: Finished reading cache file.
I0000 00:00:1776942012.170575 4345 multi_xplanes_to_op_stats.cc:149] ConvertMultiXSpaceToCombinedOpStatsWithCache: Overall Finished in 109.974us
I0000 00:00:1776942012.170631 4345 xplane_to_tools_data_with_profile_processor.cc:170] Total time for tool kernel_stats: 174.704us session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_uh4FCm/plugins/profile/2026_04_23_11_00_12
I0000 00:00:1776942012.303414 4345 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_uh4FCm/plugins/profile/2026_04_23_11_00_12
I0000 00:00:1776942012.303444 4345 xplane_to_tools_data_with_profile_processor.cc:165] Using local processing for tool: framework_op_stats
I0000 00:00:1776942012.303447 4345 multi_xplanes_to_op_stats.cc:118] ConvertMultiXSpaceToCombinedOpStatsWithCache: Started
I0000 00:00:1776942012.303505 4345 multi_xplanes_to_op_stats.cc:126] ConvertMultiXSpaceToCombinedOpStatsWithCache: Cache hit, reading binary proto
I0000 00:00:1776942012.303553 4345 multi_xplanes_to_op_stats.cc:131] ConvertMultiXSpaceToCombinedOpStatsWithCache: Finished reading cache file.
I0000 00:00:1776942012.303555 4345 multi_xplanes_to_op_stats.cc:149] ConvertMultiXSpaceToCombinedOpStatsWithCache: Overall Finished in 108.551us
I0000 00:00:1776942012.303692 4345 xplane_to_tools_data_with_profile_processor.cc:170] Total time for tool framework_op_stats: 251.747us session_id: /home/runner/.julia/scratchspaces/3c362404-f566-11ee-1572-e11a4b42c853/reactant_profiling/jl_uh4FCm/plugins/profile/2026_04_23_11_00_12
╔================================================================================╗
║ SUMMARY ║
╚================================================================================╝
AggregateProfilingResult(
runtime = 0.00007247s,
compile_time = 0.11550025s, # 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}:
11.1648 -19.3788
-13.4169 23.5148
-1.35394 -0.246291
-17.0196 -3.49616
5.61122 -11.9347
-2.20572 -13.739
6.15446 -9.27385
14.6265 5.20237
-1.9113 20.3838
12.9866 -0.926528Running 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.