CI: kernel: use ccache to speedup workflow

Use ccache to speedup kernel compilation.
Ccache dir is cached across each build test. To refresh ccache directory
we generate an hash of the kernel include files, that includes the
kernel versions of every kernel supported and the kernel compile
includes.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>

diff --git a/.github/workflows/kernel.yml b/.github/workflows/kernel.yml
index 6c8ad68438d7259e57b39677a1961a943f90c88d..0ba8c27e2e7313f88dd5dee9b55ba2dbc5dcaa73 100644 (file)
--- a/.github/workflows/kernel.yml
+++ b/.github/workflows/kernel.yml
@@ -18,6 +18,7 @@ jobs:
     outputs:
       target: ${{ steps.find_targets.outputs.target }}
       owner_lc: ${{ steps.lower_owner.outputs.owner_lc }}
+      ccache_hash: ${{ steps.ccache_hash.outputs.ccache_hash }}
 
     steps:
       - name: Checkout
@@ -30,6 +31,13 @@ jobs:
             | tr '[:upper:]' '[:lower:]')
           echo "::set-output name=owner_lc::$OWNER_LC"
 
+      - name: Generate ccache hash
+        id: ccache_hash
+        run: |
+          CCACHE_HASH=$(md5sum include/kernel-* | awk '{ print $1 }' \
+           | md5sum | awk '{ print $1 }')
+          echo "::set-output name=ccache_hash::$CCACHE_HASH"
+
       - name: Set targets
         id: find_targets
         run: |
@@ -133,6 +141,14 @@ jobs:
           path: openwrt/${{ env.TOOLCHAIN_FILE }}
           key: ${{ env.TOOLCHAIN_FILE }}-${{ env.TOOLCHAIN_SHA256 }}
 
+      - name: Cache ccache
+        uses: actions/cache@v3
+        with:
+          path: openwrt/.ccache
+          key: ccache-kernel-${{ env.TARGET }}/${{ env.SUBTARGET }}-${{ needs.determine_targets.outputs.ccache_hash }}
+          restore-keys: |
+            ccache-kernel-${{ env.TARGET }}/${{ env.SUBTARGET }}-
+
       - name: Download external toolchain
         if: ${{ steps.cache-external-toolchain.outputs.cache-hit != 'true' }}
         shell: su buildbot -c "sh -e {0}"
@@ -153,6 +169,7 @@ jobs:
           echo CONFIG_ALL_KMODS=y >> .config
           echo CONFIG_DEVEL=y >> .config
           echo CONFIG_AUTOREMOVE=y >> .config
+          echo CONFIG_CCACHE=y >> .config
 
           ./scripts/ext-toolchain.sh \
             --toolchain ${{ env.TOOLCHAIN_FILE }}/toolchain-* \