From 371ca6d4b2f9dbb0a0b012a7a8e2bad26cfd402b Mon Sep 17 00:00:00 2001
From: John Barboza <jbarboza@ca.ibm.com>
Date: Thu, 9 Mar 2017 19:57:28 -0500
Subject: [PATCH] zos: read more accurate rss info from RSM

More accurate Resident Set Size (Central Storage size on Z)
is stored in the MVS Data Areas managed by the RSM (Real
Storage Manager).

PR-URL: https://github.com/libuv/libuv/pull/1244
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
---
 src/unix/os390.c | 27 ++++++++++++++++++++++-----
 1 file changed, 22 insertions(+), 5 deletions(-)

diff --git a/src/unix/os390.c b/src/unix/os390.c
index e0a70024..80e01f3c 100644
--- a/src/unix/os390.c
+++ b/src/unix/os390.c
@@ -33,6 +33,7 @@
 #endif
 
 #define CVT_PTR           0x10
+#define PSA_PTR           0x00
 #define CSD_OFFSET        0x294
 
 /*
@@ -70,6 +71,18 @@
 /* CPC model length from the CSRSI Service. */
 #define CPCMODEL_LENGTH   16
 
+/* Pointer to the home (current) ASCB. */
+#define PSAAOLD           0x224
+
+/* Pointer to rsm address space block extension. */
+#define ASCBRSME          0x16C
+
+/*
+    NUMBER OF FRAMES CURRENTLY IN USE BY THIS ADDRESS SPACE.
+    It does not include 2G frames.
+*/
+#define RAXFMCT           0x2C
+
 /* Thread Entry constants */
 #define PGTH_CURRENT  1
 #define PGTH_LEN      26
@@ -342,13 +355,17 @@ uint64_t uv_get_total_memory(void) {
 
 
 int uv_resident_set_memory(size_t* rss) {
-  W_PSPROC buf;
+  char* psa;
+  char* ascb;
+  char* rax;
+  size_t nframes;
 
-  memset(&buf, 0, sizeof(buf));
-  if (w_getpsent(0, &buf, sizeof(W_PSPROC)) == -1)
-    return -EINVAL;
+  psa = PSA_PTR;
+  ascb  = *(char* __ptr32 *)(psa + PSAAOLD);
+  rax = *(char* __ptr32 *)(ascb + ASCBRSME);
+  nframes = *(unsigned int*)(rax + RAXFMCT);
 
-  *rss = buf.ps_size;
+  *rss = nframes * sysconf(_SC_PAGESIZE);
   return 0;
 }