[COUCHDB-3251] Remove hot loop usage of filename:rootname/1

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Component/s: Database Core
• Assignee: Unassigned
• Reporter: Paul Joseph Davis
• Created: 06/Dec/16 19:35
• Updated: 07/Dec/16 17:13
• Resolved: 07/Dec/16 17:12

Description

We added a call to filename:rootname/1 that removes the ".couch" extension when it exists. We've been doing some profiling of CouchDB 2.0 recently and found this to be a fairly expensive call. It and related calls are in the top few most expensive functions according to eprof (this is VM wide, so not just cherry picking couch_server where its actually even worse).

lists:zip/2                                                             157491702  1.35   77463688  [      0.49]
erlang:setelement/3                                                     139509262  1.48   85212600  [      0.61]
erlang:term_to_binary/2                                                  14724676  1.52   87419458  [      5.94]
erlang:phash/2                                                           30943420  1.54   88195214  [      2.85]
erlang:send/3                                                            13487486  2.06  118261137  [      8.77]
filename:rootname/4                                                     514574672  2.59  148907072  [      0.29]
ets:lookup/2                                                             32852756  2.66  152952875  [      4.66]
erts_internal:port_command/3                                             10448091  2.95  169649699  [     16.24]
ioq_server:matching_request/4                                           906453003  3.19  183041235  [      0.20]
ioq_server:split/4                                                      535820540  3.31  189913578  [      0.35]
snappy:compress/1                                                         7950803  3.42  196220575  [     24.68]
filename:do_flatten/2                                                   516517594  4.21  241562020  [      0.47]
gen_server:try_handle_call/4                                              9529789  5.66  324927694  [     34.10]
gen_server:loop/6                                                        16844687  7.41  425628355  [     25.27]

There's an obvious easy way to optimize this by using binary matching so simple PR is incoming.

Issue Links

• links to: GitHub Pull Request #217