D25079: [CopyJob] Increase the amount of data sendfile can copy at once

[Méven Car]

meven created this revision.
meven added reviewers: dfaure, Frameworks, davidedmundson.
Herald added a project: Frameworks.
Herald added a subscriber: kde-frameworks-devel.
meven requested review of this revision.

REVISION SUMMARY
  We had a bad value of 32,768 bytes to copy at once.
  But Linux sendfile can support 2,147,479,552 bytes at once.

TEST PLAN
  Tested on my system a fast drive : nvme ssd.
  
  ll test.mkv
  .rw-rw-r--  4,3G meven 30 oct.  16:16 test.mkv
  
  Before:
  time KDE_FORK_SLAVES=1 /usr/bin/kioclient5 cp file:///home/meven/test.mkv file:///home/meven/testa.mkv
  
  real    0m19,583s
  user    0m0,084s
  sys     0m0,060s
  
  After:
  
  time KDE_FORK_SLAVES=1  /home/meven/kde/usr/bin/kioclient5 cp file:///home/meven/test.mkv file:///home/meven/testa.mkv
  
  real    0m18,488s
  user    0m0,075s
  sys     0m0,046s
  
  For reference cp:
  time cp test.mkv testa.mkv
  
  real    0m18,707s
  user    0m0,062s
  sys     0m7,017s
  
  We can be as fast as cp with this, a 5.5% spead increase of large file copy.
  Results depend on your system.

REPOSITORY
  R241 KIO

BRANCH
  master

REVISION DETAIL
  https://phabricator.kde.org/D25079

AFFECTED FILES
  src/ioslaves/file/file_unix.cpp

To: meven, dfaure, #frameworks, davidedmundson
Cc: kde-frameworks-devel, LeGast00n, GB_2, michaelh, ngraham, bruns
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