HDDS-16323. StreamBlockInputStream: refill the pre-read window in bulk instead of once per response - #11159
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ss77892 wants to merge 2 commits into
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HDDS-16323. StreamBlockInputStream: refill the pre-read window in bulk instead of once per response#11159ss77892 wants to merge 2 commits into
ss77892 wants to merge 2 commits into
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chihsuan
approved these changes
Aug 30, 2026
| final long preReadLength = preRead ? preReadSize : 0; | ||
| // Refill the pre-read window in bulk once it drains below half, instead of after every response. | ||
| // Safe to skip: required <= 0 means the DataNode still owes bytes that poll() is waiting for. | ||
| if (required <= 0 && requestedLength - position >= preReadLength / 2) { |
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nit: Just a thought, what do you think about giving the / 2 a name? A named constant might make the half-window trigger easier to spot later.
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Sure. I've added preReadRefillThreshold that is computed alongside preReadSize, so the test can reference the same value rather than repeating the / 2.
chungen0126
self-requested a review
August 31, 2026 09:50
…k instead of once per response
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What changes were proposed in this pull request?
StreamBlockInputStream: refill the pre-read window in bulk instead of once per response
This change adds an early return in readBlock(): when the caller's read is already covered by what has been requested (required <= 0) and the outstanding pre-read window is still at least half full, no new request is sent. The window is refilled in bulk only once it drains below half. When required > 0 the request is always sent, so a read that needs bytes beyond the requested range is never starved.
A unit test (testPreReadWindowIsRefilledInBulk) reads a block one response at a time, as KeyInputStream does, and checks that the number of ReadBlock requests is bounded by the number of half windows and that every request carries at least half a window.
What is the link to the Apache JIRA
https://issues.apache.org/jira/browse/HDDS-16323
How was this patch tested?
UT added/ CI
Performance evaluation on 3 node cluster.
HDDS-16323.pdf