D27504: WIP: RFC: smb faster copy to local

[Harald Sitter]

sitter created this revision.
sitter added reviewers: ngraham, cfeck.
Herald added projects: Dolphin, Frameworks.
Herald added subscribers: kfm-devel, kde-frameworks-devel.
sitter requested review of this revision.

REVISION SUMMARY
  see https://bugs.kde.org/show_bug.cgi?id=291835#c57 for background
  
  - reading now happens inside a future. should be safe since we don't have any other threads doing anything while we wait.
  - the future feeds into a buffer from which the main thread will take file segments and write them to disk
  - buffer has 4 segments and synchronizes the threads via wait conditions
  - the size of a segment is determined somewhat dynamically between 64kb and 4mb. the larger a file is the more it benefits from larger read requests
  
  under perfect conditions this yields approximately mount-level copy
  performance, unfortunately those are hard to hit so on average it's usually
  less (somewhere in the range of 10 to 20% depending on the actual file
  size and server type).
  
  compared to the old code this should more or less always be 100% faster for
  large files.
  
  multiple small files should see an equal improvement from what I've seen
  copying my kio-extras dir around.
  
  for some reason gains seem much greater against win10 servers, though that
  may be because the test systems I've set up are not having equivalent IO
  capabilities.
  
  in general, all of the above only applies to cases where the server's disk
  output will be able to saturate the request volume.
  
  TODO: this probably also needs extending to smbCopy (remote<->remote) and
  smbCopyPut (local->remote). smbcopy may need to not have threading though
  since we'd use the same smb_context in two threads

TEST PLAN
  - fallocate -l 1G file
  - copy around
  - copy kio-extras around

REPOSITORY
  R320 KIO Extras

BRANCH
  thread-read

REVISION DETAIL
  https://phabricator.kde.org/D27504

AFFECTED FILES
  smb/kio_smb_dir.cpp

To: sitter, ngraham, cfeck
Cc: kde-frameworks-devel, kfm-devel, pberestov, iasensio, fprice, LeGast00n, cblack, MrPepe, fbampaloukas, alexde, GB_2, Codezela, feverfew, meven, michaelh, spoorun, navarromorales, firef, ngraham, andrebarros, bruns, emmanuelp, mikesomov
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