pkg/kconfig: rewrite Minimize()

1) Use the generic bisection implementation in pkg/bisect. It adds the
   support of identifying several necessary config diffs at once.
2) For now, limit the number of minimization iterations to 6. It's a
   lengthy process and we don't want to spend too much time doing this.
3) Bisect over leaf configuration options -- that is, those no other
   config depends upon. This should make diff split during bisection
   more reliable.
4) Save all intermediate configs to the debug files folder.

1 files changed, 7 insertions, 1 deletions

diff --git a/pkg/vcs/linux.go b/pkg/vcs/linux.go
index c6effd58a..341e488f4 100644
--- a/pkg/vcs/linux.go
+++ b/pkg/vcs/linux.go
@@ -379,7 +379,13 @@ type minimizeLinuxCtx struct {
 func (ctx *minimizeLinuxCtx) minimizeAgainst(base *kconfig.ConfigFile) error {
 	base = base.Clone()
 	ctx.transform(base)
-	minConfig, err := ctx.kconf.Minimize(base, ctx.config, ctx.pred, ctx)
+	// Don't do too many minimization runs, it will make bug bisections too long.
+	// The purpose is only to reduce the number of build/boot/test errors due to bugs
+	// in unrelated parts of the kernel.
+	// Bisection is not getting much faster with smaller configs, only more reliable,
+	// so there's a trade-off. Try to do best in 5 iterations, that's about 1.5 hours.
+	const minimizeRuns = 5
+	minConfig, err := ctx.kconf.Minimize(base, ctx.config, ctx.pred, minimizeRuns, ctx)
 	if err != nil {
 		return err
 	}