Listing of Trashbin Items Slow

[dragotin]

Based on findings in https://github.com/owncloud/enterprise/issues/6213 it is understood that listing the trashbin items is taking too long if a significant amount of files were deleted and are in the trashbin.

The code is known to be not optimized. So the action to undertake is

• Check the code and find the bottlenecks
• Find a way to increase the listing performance by (probably) parallelize the reading of the items from the trashbin structure
• Propose a as small as possible code patch to fix the behaviour and increase listing performance that can be applied to the v4 code branch.

[dragonchaser]

With cs3org/reva#4374 & delay (vm nfs-server, delay via tc):

delay	edge cold	edge warm	pr cold	pr warm
2.5ms	33.5s	12.7s	20s	10.29s

[dragonchaser]

After parallelizing the globbing we end up with the following values:

delay	edge cold	edge warm	pr cold	pr warm
2.5ms	28.46s	10.58s	703ms	280ms

[micbar]

fixed and relased with ocis v4.0.4