[Bug 1862264] Re: Browsing smb share is painfully slow

[Pablo Copissa]

Looks like gio is part of glib, not gvfs, so changed the package accordingly. 
Also made clear in the title that gio vs mount is part of the issue.

** Package changed: gvfs (Ubuntu) => glib2.0 (Ubuntu)

** Summary changed:

- Browsing smb share is painfully slow
+ Browsing smb share is painfully slow when mounted via "gio" (compared with "mount")

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Title:
  Browsing smb share is painfully slow when mounted via "gio" (compared
  with "mount")

Status in glib2.0 package in Ubuntu:
  New

Bug description:
  Ubuntu 18.04 LTS here, fully updated (as of late Jan 2020).
  TEST #1:
  To establish a baseline/expected behavior, we first mount an SMB share via mount.cifs and time an ls command:
  $ sudo mount -t cifs -o username=pablo //myserver.example.com/share ~/mnt/share
  $ cd ~/mnt/share/some/dir
  $ time ls
  ... approx 320 files ...
  real	0m1,080s
  user	0m0,008s
  sys	0m0,005s
  $ sudo umount ~/mnt/share

  TEST #2
  Now we do the same via gio mount:
  $ gio mount smb://myserver.example.com/share
  cd /run/user/1000/gvfs/smb-share\:server\=myserver.example.com\,share\=share/some/dir
  $ time ls
  ... same 320 files ...
  real	0m28,999s
  user	0m0,013s
  sys	0m0,032s

  Enumeration of files is about 29 times slower when mounted via gio
  mount than via mount -t cifs.

  TEST #3
  Now for the real weird: while using the gio-mounted folder, we now time ls IN COMBINATION WITH SOMETHING ELSE (can be strace ls, ls|wc etc...):
  $ time ls | wc
     321     323    9804

  real	0m0,546s
  user	0m0,006s
  sys	0m0,004s

  Note that this is almost TWICE AS FAST than the "fast" mount of test
  #1 and about 53 times faster than "slow" test #2 !

  The expectation is that Tests 1 and 2 should have similar timings, not
  differing by a factor of 30 or so. More disturbing, there is no good
  reason why tests 2 and 3 differ by an even bigger factor of 53: They
  use the same underlying infrastructure which test 3 proves is
  adequately fast. And yet, we get this slow down in test 2.

  As a final note, these benchmarks are a distilled version of the original real-life motivating scenario where a Java-based program would simply take tens of minutes to display the same list of 320 files when mounted via gio mount and a second or so when mounted via mount -t cifs.
  The same timing difference is of course visible in any file manager.

  Hope this helps

  PS: several old/ancient bug reports exist for a similar issue and I
  deliberately copied the title from one of them (#259771)

  PS2: may or may not be relevant: The remote server is a VM running
  Windows 7 (yes, I know...) and the connection was made via VPN (Ubuntu
  stock SSTP).

  PS3: Another data point (server is now a Synolgy NAS, not a Win7 VM)

  $ gio mount smb://nas.example.com/share2

  $ cd /run/user/1000/gvfs/smb-
  share\:server\=nas.example.com\,share\=share2/another/path

  $ time ls

  ... 528 subdirs approximately ...

  real	0m45,075s
  user	0m0,013s
  sys	0m0,058s

  $ time ls | wc
      528    1631   10893

  real	0m0,911s
  user	0m0,003s
  sys	0m0,005s

  Factor is about 50.

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