Suggestions about cache handling

[mwestphal]

I tried using this action in my project but the performance are not at all what I expected.

Here is what I get:

Compile requests                   9129
Compile requests executed          9129
Cache hits                         6531
Cache hits (C/C++)                 6531
Cache misses                       2598
Cache misses (C/C++)               2598
Cache timeouts                        0
Cache read errors                     0
Forced recaches                       0
Cache write errors                    0
Compilation failures                  0
Cache errors                          0
Non-cacheable compilations            0
Non-cacheable calls                   0
Non-compilation calls                 0
Unsupported compiler calls            0
Average cache write               0.026 s
Average compiler                  4.729 s
Average cache read hit            0.034 s
Failed distributed compilations       0
Cache location                  ghac, name: sccache-v0.5.4, prefix: /sccache/
Version (client)                0.5.4

Although when I set up sccache with github cache myself, I get this:

Compile requests                   9122
Compile requests executed          9122
Cache hits                         9113
Cache hits (C/C++)                 9113
Cache misses                          9
Cache misses (C/C++)                  9
Cache timeouts                        0
Cache read errors                     0
Forced recaches                       0
Cache write errors                    0
Compilation failures                  0
Cache errors                          0
Non-cacheable compilations            0
Non-cacheable calls                   0
Non-compilation calls                 0
Unsupported compiler calls            0
Average cache write               0.000 s
Average compiler                  2.476 s
Average cache read hit            0.000 s
Failed distributed compilations       0
Cache location                  Local disk: "/github/home/.cache/sccache"
Version (client)                0.4.2
Cache size                          207 MiB
Max cache size                       10 GiB

I think this is related to the fact than I'm using a single cache file insead of hundreds as you seem to be doing.

The logic I'm using is that the cache file name contains the date of the build, like this:

  - name: Initialize sccache environnement
    shell: bash
    run: |
      echo SCCACHE_CACHE=$(sccache --show-stats | grep Local | cut -d '"' -f2) >> $GITHUB_ENV
      echo DATE_STRING=$(date +'%Y%m%d') >> $GITHUB_ENV
      sccache --stop-server

  - name: Recover sccache cache
    uses: actions/cache@v3
    with:
      path: ${{env.SCCACHE_CACHE}}
      key: sccache-cache-${{inputs.raytracing_label}}-${{runner.os}}-0-${{env.DATE_STRING}}
      restore-keys: sccache-cache-${{inputs.raytracing_label}}-${{runner.os}}-0

This means the cache is being updated everyday, and it avoids using hundreds of caches.

[sylvestre]

Bonjour Mathieu (seems that we have a few common friends ;)

as you noticed, github storage isn't doing great with multiple files. I guess it is the crux of the issue...

See mozilla/sccache#1818 & https://github.com/orgs/community/discussions/55049

[sylvestre]

anyway, dupe of
#50