Stream large files during unpacking #2707
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Fixes rust-lang#2632, rust-lang#2145, rust-lang#2564 Files over 16M are now written incrementally chunks rather than buffered in memory in one full linear buffer. This chunk size is not configurable. For threaded unpacking, the entire memory buffer will be used to buffer chunks and a single worker thread will dispatch IO operations from the buffer, so minimal performance impact should be anticipated (file size/16M round trips at worst, and most network file systems will latency hide linear writes). For immediate unpacking, each chunk is dispatched directly to disk, which may impact performance as less latency hiding is possible - but for immediate unpacking clarity of behaviour is the priority.
kinnison
suggested changes
Apr 5, 2021
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For the most part I follow this given the conversations we have had before. I like the CompletedIO approach to the budget reclaim, that refactor pleases me.
A couple of nit-picking whinges, and I'll be pretty happy. I want to play a bit with this locally though too, so even if you do the cleanups now, don't merge yet.
kinnison
approved these changes
Apr 5, 2021
This was referenced Apr 6, 2021
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Fixes #2632, #2145, #2564
Files over 16M are now written incrementally chunks rather than buffered
in memory in one full linear buffer. This chunk size is not
configurable.
For threaded unpacking, the entire memory buffer will be used to buffer
chunks and a single worker thread will dispatch IO operations from the
buffer, so minimal performance impact should be anticipated (file
size/16M round trips at worst, and most network file systems will
latency hide linear writes).
For immediate unpacking, each chunk is dispatched directly to disk,
which may impact performance as less latency hiding is possible - but
for immediate unpacking clarity of behaviour is the priority.