perf: stream SFTP uploads/downloads instead of buffering whole file#195
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Yaminyam wants to merge 1 commit intolablup:mainfrom
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perf: stream SFTP uploads/downloads instead of buffering whole file#195Yaminyam wants to merge 1 commit intolablup:mainfrom
Yaminyam wants to merge 1 commit intolablup:mainfrom
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Upload (`upload_file`, `upload_dir_recursive`) used `tokio::fs::read` to load the entire local file into a `Vec<u8>` before calling `write_all`, and download (`download_file`, `download_dir_recursive`) used `read_to_end` into a pooled buffer + `clone()` to a separate `Vec` before writing locally. For multi-GB transfers this means peak RSS scales with file size and large files OOM the client. Replace each path with a small `stream_copy()` helper that loops on 256 KiB reads and writes through the existing `AsyncRead`/`AsyncWrite` implementations on `tokio::fs::File` and `russh_sftp::client::fs::File`. Buffer size matches the SFTP MAX_WRITE_LENGTH so each chunk maps to a single SFTP packet without further fragmentation. Verified locally on macOS arm64 against `bssh-server` v2.1.3 over loopback with a 1 GiB file: | Op | Build | real | RSS | |----------|------------|---------|----------| | upload | unpatched | 38.65s | 3.23 GB | | upload | streaming | 3.47s | 20 MB | | download | unpatched | 3.93s | 2.17 GB | | download | streaming | 3.41s | 16 MB | Peak RSS drops ~160x and uploads complete ~11x faster (a single multi-MB `write_all` apparently serializes much worse through the SFTP pipeline than 256 KiB chunked writes).
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Summary
Upload (
upload_file,upload_dir_recursive) usedtokio::fs::readto load the entire local file into aVec<u8>before callingwrite_all, and download (download_file,download_dir_recursive) usedread_to_endinto a pooled buffer +clone()to a separateVecbefore writing locally. For multi-GB transfers this means peak RSS scales with file size and large files OOM the client.Replace each path with a small
stream_copy()helper that loops on 256 KiB reads and writes through the existingAsyncRead/AsyncWriteimplementations ontokio::fs::Fileandrussh_sftp::client::fs::File. Buffer size matches the SFTPMAX_WRITE_LENGTHso each chunk maps to a single SFTP packet without further fragmentation.Measured impact
Verified locally on macOS arm64 against
bssh-serverv2.1.3 over loopback with a 1 GiB file:Peak RSS drops ~160x and uploads complete ~11x faster (a single multi-MB
write_allapparently serializes much worse through the SFTP pipeline than 256 KiB chunked writes).Test plan