diff --git a/library/include/slabinfo.h b/library/include/slabinfo.h
index 128bad94..f63ca79e 100644
--- a/library/include/slabinfo.h
+++ b/library/include/slabinfo.h
@@ -40,7 +40,7 @@ enum slabinfo_item {
     SLAB_ACTIVE_SLABS,          //    u_int         "
     SLAB_PAGES_PER_SLAB,        //    u_int         "
     SLAB_PERCENT_USED,          //    u_int        derived from ACTIVE_OBJS / NUM_OBJS
-    SLAB_SIZE_TOTAL,            //   ul_int        derived from page size * NUM_OBJS * PAGES_PER_SLAB
+    SLAB_SIZE_TOTAL,            //   ul_int        derived from page size * NUMS_SLABS * PAGES_PER_SLAB
 
     SLABS_CACHES_TOTAL,         //    u_int        derived from all caches
     SLABS_CACHES_ACTIVE,        //    u_int         "
diff --git a/library/slabinfo.c b/library/slabinfo.c
index a4386d61..1d4453fd 100644
--- a/library/slabinfo.c
+++ b/library/slabinfo.c
@@ -434,6 +434,10 @@ static int parse_slabinfo20 (
         if (node->obj_size > slabs->max_obj_size)
             slabs->max_obj_size = node->obj_size;
 
+        /* cache_size is not accurate, it's the upper limit of memory used by this slab.
+         * When system using slub(most common case) is under high memory pressure, there
+         * are slab order fallbacks, which means pages_per_slab is not constant and may decrease.
+         */ 
         node->cache_size = (unsigned long)node->nr_slabs * node->pages_per_slab * page_size;
 
         if (node->nr_objs) {
diff --git a/man/slabtop.1 b/man/slabtop.1
index edf4784e..089fb0e5 100644
--- a/man/slabtop.1
+++ b/man/slabtop.1
@@ -104,7 +104,13 @@ The
 .B slabtop
 statistic header is tracking how many bytes of slabs are being
 used and is not a measure of physical memory.  The 'Slab' field in the
-\fI/proc/meminfo\fR file is tracking information about used slab physical
+\fI/proc/meminfo\fR file is tracking information about used slab physical memory.
+.PP
+The
+.B CACHE SIZE
+column is not accurate, it's the upper limit of memory used by specific slab. When system
+using slub (most common case) is under high memory pressure, there are slab order 
+fallbacks, which means "pages per slab" is not constant and may decrease.
 .SH AUTHORS
 Written by Chris Rivera and Robert Love.
 .PP