fix: update BlobReadSession ScatteringByteChannel projection to use less CPU #3324
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…ess CPU Switch to using a graceful poll of the queue rather than a spin loop poll. Elements being added to the queue will happen asynchronously from a background gRPC thread. Rather than immediately returning if the queue is empty allow waiting up to 10 microseconds (possibly not optimal duration, but testing shows good results -- before ~51% of cpu time is spent in `StreamingRead.read`, after ~13% of cpu time is spent in `StreamingRead.read` for roughly the same wall time 1.59% before, 1.52% after. This also has the added benefit of reduced perceived latency for an application. ##### profiled workload results Download 128MiB object from 0-EOF 1000 times, while async profiler is profiling `event=cpu`. Using `StorageDataClient.fastOpenReadSession` to begin the read while creating the session. All values below are latency in milliseconds | | p50 | p90 | p95 | |--------|------:|------:|------:| | before | ~ 266 | ~ 408 | ~ 468 | | after | ~ 253 | ~ 384 | ~ 431 | * Remove no longer necessary Buffers.totalRemaining call
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bajajneha27
previously approved these changes
Oct 3, 2025
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bajajneha27
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Oct 6, 2025
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Switch to using a graceful poll of the queue rather than a spin loop poll.
Elements being added to the queue will happen asynchronously from a background gRPC thread. Rather than immediately returning if the queue is empty allow waiting up to 10 microseconds (possibly not optimal duration, but testing shows good results -- before ~51% of cpu time is spent in
StreamingRead.read, after ~13% of cpu time is spent inStreamingRead.readfor roughly the same wall time 1.59% before, 1.52% after). This also has the added benefit of reduced perceived latency for an application.profiled workload results
Download 128MiB object from 0-EOF 1000 times, while async profiler is profiling
event=cpu. UsingStorageDataClient.fastOpenReadSessionto begin the read while creating the session.All values below are latency in milliseconds
async-profilers flame graphs