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SftpClient: DowloadFile does not perform well on Sun SSH #292

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drieseng opened this issue Aug 29, 2017 · 0 comments
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SftpClient: DowloadFile does not perform well on Sun SSH #292

drieseng opened this issue Aug 29, 2017 · 0 comments
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performance
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2016.1.0-beta3

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drieseng commented Aug 29, 2017 •
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While I'm seeing throughput increases of up to 50% when used with OpenSSH, the switch to a read-ahead mechanism actually regressed the throughput with Sun SSH (1.1.5).

There appear to be two causes for this:

  • Sun's SSH implementation does not seem to enjoy receiving a SSH_FXP_OPEN and a SSH_FXP_LSTAT request for a given file at the same time.
  • We performing async read-aheads until we've received a zero-length response (signaling EOF).
    This means that we risk having a few SSH_FXP_READ requests with an offset beyond EOF.
    This causes Sun SSH to take a brief moment of reflection.
@drieseng drieseng added this to the 2016.1.0-beta3 milestone Aug 29, 2017
@drieseng drieseng self-assigned this Aug 29, 2017
@drieseng drieseng mentioned this issue Aug 29, 2017
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drieseng added a commit that referenced this issue Sep 15, 2017
@drieseng
Avoid overlapping SSH_FXP_OPEN and SSH_FXP_LSTAT requests for the sam…
80ae79c 
…e file as this causes a performance degradation on Sun SSH.

Switch to a single (sync) read-ahead if the file size is known, and we're starting to read (ahead) past that file size.
Harden against exceptions closing the file handle in Dispose

Fixes issue #292.
@sterlind sterlind mentioned this issue Oct 5, 2019
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