support print hooks before running.

[mzr1996]

Motivation

Now, hooks are added in silence, so it's not convenient to observe which hooks are used and the execution order.

Modification

This PR will print stage-wise hook info in the order of execution and print their priority, like

2021-06-22 16:10:31,951 - mmcls - INFO - Start running, host: xxx, work_dir: /home/xxx/work_dirs
2021-06-22 16:10:31,951 - mmcls - INFO - Use hooks (Hooks will be executed in the following order):
before_run:
(VERY_HIGH   ) CosineAnnealingLrUpdaterHook       
(NORMAL      ) CheckpointHook                     
(NORMAL      ) EvalHook                           
(VERY_LOW    ) TextLoggerHook                     
 -------------------- 
before_train_epoch:
(VERY_HIGH   ) CosineAnnealingLrUpdaterHook       
(NORMAL      ) EvalHook                           
(LOW         ) IterTimerHook                      
(VERY_LOW    ) TextLoggerHook                     
 -------------------- 
before_train_iter:
(VERY_HIGH   ) CosineAnnealingLrUpdaterHook       
(NORMAL      ) EvalHook                           
(LOW         ) IterTimerHook                      
 -------------------- 
after_train_iter:
(ABOVE_NORMAL) OptimizerHook                      
(NORMAL      ) CheckpointHook                     
(NORMAL      ) EvalHook                           
(LOW         ) IterTimerHook                      
(VERY_LOW    ) TextLoggerHook                     
 -------------------- 
after_train_epoch:
(NORMAL      ) CheckpointHook                     
(NORMAL      ) EvalHook                           
(VERY_LOW    ) TextLoggerHook                     
 -------------------- 
before_val_epoch:
(LOW         ) IterTimerHook                      
(VERY_LOW    ) TextLoggerHook                     
 -------------------- 
before_val_iter:
(LOW         ) IterTimerHook                      
 -------------------- 
after_val_iter:
(LOW         ) IterTimerHook                      
 -------------------- 
after_val_epoch:
(VERY_LOW    ) TextLoggerHook                     
 -------------------- 
2021-06-22 16:10:31,951 - mmcls - INFO - workflow: [('train', 1)], max: 300 epochs

Checklist

1. Pre-commit or other linting tools are used to fix the potential lint issues.
2. The modification is covered by complete unit tests. If not, please add more unit test to ensure the correctness.
3. If the modification has potential influence on downstream projects, this PR should be tested with downstream projects, like MMDet or MMCls.
4. The documentation has been modified accordingly, like docstring or example tutorials.

[codecov]

Codecov Report

Merging #1123 (40a1d7b) into master (eb08835) will increase coverage by 0.20%.
The diff coverage is 95.45%.

❗ Current head 40a1d7b differs from pull request most recent head 98f488d. Consider uploading reports for the commit 98f488d to get more accurate results

@@            Coverage Diff             @@
##           master    #1123      +/-   ##
==========================================
+ Coverage   67.74%   67.95%   +0.20%     
==========================================
  Files         159      159              
  Lines       10337    10417      +80     
  Branches     1873     1896      +23     
==========================================
+ Hits         7003     7079      +76     
- Misses       2966     2969       +3     
- Partials      368      369       +1     

Flag	Coverage Δ
unittests	67.95% <95.45%> (+0.20%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
mmcv/utils/__init__.py	88.23% <ø> (ø)
mmcv/runner/base_runner.py	78.30% <92.30%> (+0.83%)	⬆️
mmcv/utils/config.py	90.38% <94.87%> (+0.50%)	⬆️
mmcv/runner/epoch_based_runner.py	82.85% <100.00%> (+0.16%)	⬆️
mmcv/runner/hooks/hook.py	96.29% <100.00%> (+0.94%)	⬆️
mmcv/runner/iter_based_runner.py	57.14% <100.00%> (+0.30%)	⬆️
mmcv/runner/priority.py	71.42% <100.00%> (+3.00%)	⬆️
mmcv/utils/misc.py	95.23% <100.00%> (+0.23%)	⬆️

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