Refactor fellow_cache_obj_lru_touch and count touches

src/fellow_cache.c

@@ -626,6 +626,7 @@ struct fellow_cache_obj {
 	enum fcol_state			logstate;
 
 	struct fellow_cache_lru		*lru;
+	uint64_t			ntouched;
 
 	struct buddy_ptr_page		fco_mem;	// nil == embedded
 
@@ -3486,7 +3487,7 @@ fellow_cache_obj_lru_touch(struct fellow_cache_obj *fco)
 {
 	struct fellow_cache_lru *lru;
 	struct fellow_cache_seg *fcs;
-	int r;
+	int r = 0;
 
 	CHECK_OBJ_NOTNULL(fco, FELLOW_CACHE_OBJ_MAGIC);
 	lru = fco->lru;
@@ -3495,11 +3496,12 @@ fellow_cache_obj_lru_touch(struct fellow_cache_obj *fco)
 	CHECK_OBJ_NOTNULL(fcs, FELLOW_CACHE_SEG_MAGIC);
 
 	if (! fcs->fcs_onlru)
-		return (0);
+		goto out;
 
+	r = 1;
 	// mutate should be failing, so it will do the lru move
 	if (fcs->fco_lru_mutate)
-		return (1);
+		goto out;
 
 	assert(fellow_cache_shouldlru(fcs->state, fco->oc, fcs->refcnt));
 
@@ -3515,7 +3517,12 @@ fellow_cache_obj_lru_touch(struct fellow_cache_obj *fco)
 	//lint -e{455} flexelint does not grok trylock
 	AZ(pthread_mutex_unlock(&lru->lru_mtx));
 
-	return (1);
+	r = 1;
+  out:
+	// deliberately unlocked, not critical if update is missed
+	fco->ntouched++;
+
+	return (r);
 }
 
 // not unter logmtx
@@ -6168,7 +6175,7 @@ t_cache(const char *fn, unsigned chksum)
 
 	// canary so size increase does not happen unnoticed
 	sz  = sizeof(struct fellow_cache_obj);
-	assert(sz <= 328);
+	assert(sz <= 352);
 
 	AZ(stvfe_tune_init(tune, memsz, dsksz, objsize_hint));
 	tune->hash_obj = chksum;