syz-ci: flush coverage report generator

Flush manager coverage report generator after requesting JSONL report.
We won't use coverage reports after this point, but it consumes gigs of RAM.

3 files changed, 35 insertions, 15 deletions

diff --git a/syz-ci/manager.go b/syz-ci/manager.go
index 542d3950e..38fcc4a77 100644
--- a/syz-ci/manager.go
+++ b/syz-ci/manager.go
@@ -877,7 +877,10 @@ func (mgr *Manager) uploadCoverStat(fuzzingMinutes int) error {
 	}
 	defer buildSem.Signal()
 
-	resp, err := mgr.httpGET("/cover?jsonl=1")
+	// Coverage report generation consumes and caches lots of memory.
+	// In the syz-ci context report generation won't be used after this point,
+	// so tell manager to flush report generator.
+	resp, err := mgr.httpGET("/cover?jsonl=1&flush=1")
 	if err != nil {
 		return fmt.Errorf("failed to httpGet /cover?jsonl=1 report: %w", err)
 	}
diff --git a/syz-manager/cover.go b/syz-manager/cover.go
index 9591562b0..31fabeca9 100644
--- a/syz-manager/cover.go
+++ b/syz-manager/cover.go
@@ -12,19 +12,30 @@ import (
 	"github.com/google/syzkaller/pkg/mgrconfig"
 )
 
-var getReportGenerator = func() func(cfg *mgrconfig.Config,
-	modules []host.KernelModule) (*cover.ReportGenerator, error) {
-	var once sync.Once
-	var rg *cover.ReportGenerator
-	var err error
-	return func(cfg *mgrconfig.Config, modules []host.KernelModule) (*cover.ReportGenerator, error) {
-		once.Do(func() {
-			log.Logf(0, "initializing coverage information...")
-			rg, err = cover.MakeReportGenerator(cfg, cfg.KernelSubsystem, modules, cfg.RawCover)
-		})
-		return rg, err
+var (
+	cachedRepGenMu sync.Mutex
+	cachedRepGen   *cover.ReportGenerator
+)
+
+func getReportGenerator(cfg *mgrconfig.Config, modules []host.KernelModule) (*cover.ReportGenerator, error) {
+	cachedRepGenMu.Lock()
+	defer cachedRepGenMu.Unlock()
+	if cachedRepGen == nil {
+		log.Logf(0, "initializing coverage information...")
+		rg, err := cover.MakeReportGenerator(cfg, cfg.KernelSubsystem, modules, cfg.RawCover)
+		if err != nil {
+			return nil, err
+		}
+		cachedRepGen = rg
 	}
-}()
+	return cachedRepGen, nil
+}
+
+func resetReportGenerator() {
+	cachedRepGenMu.Lock()
+	defer cachedRepGenMu.Unlock()
+	cachedRepGen = nil
+}
 
 func coverToPCs(rg *cover.ReportGenerator, cov []uint32) []uint64 {
 	pcs := make([]uint64, 0, len(cov))
diff --git a/syz-manager/http.go b/syz-manager/http.go
index ddb0707f1..a8c9a8ccd 100644
--- a/syz-manager/http.go
+++ b/syz-manager/http.go
@@ -14,7 +14,7 @@ import (
 	"os"
 	"path/filepath"
 	"regexp"
-	"runtime"
+	"runtime/debug"
 	"sort"
 	"strconv"
 	"strings"
@@ -267,6 +267,13 @@ func (mgr *Manager) httpCoverCover(w http.ResponseWriter, r *http.Request, funcF
 		return
 	}
 
+	if r.FormValue("flush") != "" {
+		defer func() {
+			resetReportGenerator()
+			debug.FreeOSMemory()
+		}()
+	}
+
 	mgr.mu.Lock()
 	var progs []cover.Prog
 	if sig := r.FormValue("input"); sig != "" {
@@ -343,7 +350,6 @@ func (mgr *Manager) httpCoverCover(w http.ResponseWriter, r *http.Request, funcF
 		http.Error(w, fmt.Sprintf("failed to generate coverage profile: %v", err), http.StatusInternalServerError)
 		return
 	}
-	runtime.GC()
 }
 
 func (mgr *Manager) httpCoverFallback(w http.ResponseWriter, r *http.Request) {