--- a/agent/mibgroup/hardware/memory/memory_linux.c
+++ b/agent/mibgroup/hardware/memory/memory_linux.c
@@ -24,7 +24,8 @@
     static int   first = 1;
     ssize_t      bytes_read;
     char        *b;
-    unsigned long memtotal = 0,  memfree = 0, memshared = 0,
+    int          have_memavail = 0;
+    unsigned long memtotal = 0,  memavail = 0, memfree = 0, memshared = 0,
                   buffers = 0,   cached = 0, sreclaimable = 0,
                   swaptotal = 0, swapfree = 0;
 
@@ -81,6 +82,11 @@
         if (first)
             snmp_log(LOG_ERR, "No MemTotal line in /proc/meminfo\n");
     }
+    b = strstr(buff, "MemAvailable: ");
+    if (b) {
+        have_memavail = 1;
+        sscanf(b, "MemAvailable: %lu", &memavail);
+    }
     b = strstr(buff, "MemFree: ");
     if (b) 
         sscanf(b, "MemFree: %lu", &memfree);
@@ -151,6 +157,18 @@
         mem->other = -1;
     }
 
+    if (have_memavail) {
+        mem = netsnmp_memory_get_byIdx(NETSNMP_MEM_TYPE_AVAILMEM, 1);
+        if (mem) {
+            if (!mem->descr)
+                mem->descr = strdup("Available memory");
+            mem->units = 1024;
+            mem->size  = memavail;
+            mem->free  = memavail;
+            mem->other = -1;
+        }
+    }
+
     mem = netsnmp_memory_get_byIdx( NETSNMP_MEM_TYPE_VIRTMEM, 1 );
     if (!mem) {
         snmp_log_perror("No Virtual Memory info entry");
--- a/agent/mibgroup/ucd-snmp/memory.c
+++ b/agent/mibgroup/ucd-snmp/memory.c
@@ -26,7 +26,7 @@
         netsnmp_create_handler_registration("memory", handle_memory,
                                  memory_oid, OID_LENGTH(memory_oid),
                                              HANDLER_CAN_RONLY),
-                                 1, 26);
+                                 1, 27);
     netsnmp_register_scalar(
         netsnmp_create_handler_registration("memSwapError", handle_memory,
                            memSwapError_oid, OID_LENGTH(memSwapError_oid),
@@ -271,6 +271,16 @@
             val *= (mem_info->units/1024);
 	    c64.low = val & 0xFFFFFFFF;
 	    c64.high = val >>32;
+            break;
+        case MEMORY_SYS_AVAIL:
+	    type = ASN_COUNTER64;
+            mem_info = netsnmp_memory_get_byIdx(NETSNMP_MEM_TYPE_AVAILMEM, 0);
+            if (!mem_info)
+                goto NOSUCH;
+            val = mem_info->size;       /* memavail */
+            val *= (mem_info->units/1024);
+	    c64.low = val & 0xFFFFFFFF;
+	    c64.high = val >> 32;
             break;
         case MEMORY_SWAP_ERROR:
             mem_info = netsnmp_memory_get_byIdx( NETSNMP_MEM_TYPE_SWAP, 0 );
--- a/agent/mibgroup/ucd-snmp/memory.h
+++ b/agent/mibgroup/ucd-snmp/memory.h
@@ -41,6 +41,7 @@
 #define MEMORY_SHARED_X     24
 #define MEMORY_BUFFER_X     25
 #define MEMORY_CACHED_X     26
+#define MEMORY_SYS_AVAIL    27
 #define MEMORY_SWAP_ERROR  100
 #define MEMORY_SWAP_ERRMSG 101
 #endif                          /* MEMORY_H */
--- ./include_orig/net-snmp/agent/hardware/memory.h     2020-11-26 06:06:36.460871546 +0800
+++ ./include/net-snmp/agent/hardware/memory.h  2020-11-26 06:08:47.210291823 +0800
@@ -10,6 +10,7 @@
 #define NETSNMP_MEM_TYPE_SHARED   8
 #define NETSNMP_MEM_TYPE_SHARED2  9
 #define NETSNMP_MEM_TYPE_SWAP    10
+#define NETSNMP_MEM_TYPE_AVAILMEM 11
     /* Leave space for individual swap devices */
 #define NETSNMP_MEM_TYPE_MAX     30

--- a/mibs/UCD-SNMP-MIB.txt
+++ b/mibs/UCD-SNMP-MIB.txt
@@ -745,6 +745,22 @@
          underlying operating system does not explicitly identify
          memory as specifically reserved for this purpose."
     ::= { memory 26 }
+
+memSysAvail OBJECT-TYPE
+    SYNTAX	CounterBasedGauge64
+    UNITS       "kB"
+    MAX-ACCESS	read-only
+    STATUS	current
+    DESCRIPTION
+        "The total amount of available memory, which is an estimate
+         of how much memory is available for starting new applications,
+         without swapping.
+
+         This object will not be implemented on hosts where the
+         underlying operating system does not explicitly identify
+         memory as specifically reserved for this purpose."
+    ::= { memory 27 }
+
 
 memSwapError OBJECT-TYPE
     SYNTAX	UCDErrorFlag