top: exploit new kb_main_available, make Jaromir happy

This patch will trade a former pessimistic calculation
of free physical memory for a more optimistic one that
uses the newly added kb_main_available library export.

But in case one might wish to return to the old former
method, there's a new #define that was made available.

[ the new calculation will affect graphing mode only ]

Reference(s):
http://www.freelists.org/post/procps/systemd-support-to-library,9

Signed-off-by: Jim Warner <james.warner@comcast.net>

top/top.1

@@ -470,14 +470,21 @@ with the `E' \*(CI.
 
 As a default, Line 1 reflects \*(MP, classified as:
 .nf
-    total, used, free and buffers
+    total, free, used and buff/cache
 .fi
 
 Line 2 reflects mostly \*(MV, classified as:
 .nf
-    total, used, free and cached (which is \*(MP)
+    total, free, used and avail (which is \*(MP)
 .fi
 
+The \fBavail\fR number on line 2 is an estimation of \*(MP available for
+starting new applications, without swapping.
+Unlike the \fBfree\fR field, it attempts to account for readily reclaimable
+page cache and memory slabs.
+It is available on kernels 3.14, emulated on kernels 2.6.27+ and displayed
+as zero otherwise.
+
 In the alternate memory display modes, two abbreviated summary lines
 are shown consisting of these elements:
 .nf
@@ -489,9 +496,10 @@ are shown consisting of these elements:
 Where: a) is the percentage used; b) is the total available; and c) is one of two
 visual graphs of those representations.
 
-In the case of \*(MP, the percentage includes the sum of \fBused\fR, \fBbuffers\fR
+In the case of \*(MP, the percentage represents the \fBtotal\fR minus the estimated
-and \fBcached\fR memory noted above.
+\fBavail\fR noted above.
-The `Mem' graph itself is divided between \fBused\fR then \fBbuffers\fR and \fBcached\fR combined.
+The `Mem' graph itself is divided between \fBused\fR the any remaining memory not
+otherwise accounted for by \fBavail\fR.
 \*(XT 4b. SUMMARY AREA Commands and the `m' command for additional information
 on that special 4-way toggle.
 

top/top.c

@@ -5216,7 +5216,7 @@ numa_nope:
       // and prT macro might replace space at buf[8] with:   ------> +
          char buf[10]; // MEMORY_lines_fmt provides for 8+1 bytes
       } buftab[8];
-      unsigned long kb_main_my_used;
+      unsigned long kb_main_my_used, kb_main_my_misc;
 
       if (!scaletab[0].label) {
          scaletab[0].label = N_txt(AMT_kilobyte_txt);
@@ -5226,7 +5226,8 @@ numa_nope:
          scaletab[4].label = N_txt(AMT_petabyte_txt);
          scaletab[5].label = N_txt(AMT_exxabyte_txt);
       }
-      kb_main_my_used = kb_main_used - kb_main_buffers - kb_main_cached;
+      kb_main_my_misc = kb_main_buffers + kb_main_cached;
+      kb_main_my_used = kb_main_used - kb_main_my_misc;
 
       if (w->rc.graph_mems) {
          static struct {
@@ -5238,7 +5239,11 @@ numa_nope:
          char used[SMLBUFSIZ], util[SMLBUFSIZ], dual[MEDBUFSIZ];
          int ix = w->rc.graph_mems - 1;
          float pct_used = (float)kb_main_my_used * (100.0 / (float)kb_main_total),
-               pct_misc = (float)(kb_main_buffers + kb_main_cached) * (100.0 / (float)kb_main_total),
+#ifdef MEMGRAPH_OLD
+               pct_misc = (float)kb_main_my_misc * (100.0 / (float)kb_main_total),
+#else
+               pct_misc = (float)(kb_main_total - kb_main_available - kb_main_my_used) * (100.0 / (float)kb_main_total),
+#endif
                pct_swap = kb_swap_total ? (float)kb_swap_used * (100.0 / (float)kb_swap_total) : 0;
          snprintf(used, sizeof(used), gtab[ix].used, (int)((pct_used * Graph_adj) + .5), gtab[ix].type);
          snprintf(util, sizeof(util), gtab[ix].misc, (int)((pct_misc * Graph_adj) + .5), gtab[ix].type);
@@ -5250,9 +5255,9 @@ numa_nope:
             , scT(label), N_txt(WORD_abv_swp_txt), pct_swap, bfT(1), Graph_len +2, Graph_len +2, util));
       } else {
          prT(bfT(0), mkM(total));   prT(bfT(1), mkM(free));
-         prT(bfT(2), mkM(my_used)); prT(bfT(3), mkM(buffers));
+         prT(bfT(2), mkM(my_used)); prT(bfT(3), mkM(my_misc));
          prT(bfT(4), mkS(total));   prT(bfT(5), mkS(free));
-         prT(bfT(6), mkS(used));    prT(bfT(7), mkM(cached));
+         prT(bfT(6), mkS(used));    prT(bfT(7), mkM(available));
          show_special(0, fmtmk(N_unq(MEMORY_lines_fmt)
             , scT(label), N_txt(WORD_abv_mem_txt), bfT(0), bfT(1), bfT(2), bfT(3)
             , scT(label), N_txt(WORD_abv_swp_txt), bfT(4), bfT(5), bfT(6), bfT(7)

top/top.h

@@ -41,6 +41,7 @@
 //#define INSP_OFFDEMO            /* disable demo screens, issue msg instead */
 //#define INSP_SAVEBUF            /* preserve 'Insp_buf' contents in a file  */
 //#define INSP_SLIDE_1            /* when scrolling left/right don't move 8  */
+//#define MEMGRAPH_OLD            /* don't use 'available' when graphing Mem */
 //#define OFF_HST_HASH            /* use BOTH qsort+bsrch vs. hashing scheme */
 //#define OFF_NUMASKIP            /* do NOT skip numa nodes if discontinuous */
 //#define OFF_SCROLLBK            /* disable tty emulators scrollback buffer */
@@ -658,6 +659,9 @@ typedef struct WIN_t {
 #if defined(TERMIOS_ONLY)
 # warning 'TERMIOS_ONLY' disables input recall and makes man doc incorrect
 #endif
+#if defined(MEMGRAPH_OLD)
+# warning 'MEMGRAPH_OLD' will make the man document Section 2c. misleading
+#endif
 
 
 /*######  Some Prototypes (ha!)  #########################################*/

top/top_nls.c

@@ -637,8 +637,8 @@ static void build_uniq_nlstab (void) {
       "%#5.1f ~2us,~3%#5.1f ~2sy,~3%#5.1f ~2ni,~3%#5.1f ~2id,~3%#5.1f ~2wa,~3%#5.1f ~2hi,~3%#5.1f ~2si,~3%#5.1f ~2st~3\n");
 
    Uniq_nlstab[MEMORY_lines_fmt] = _(""
-      "%s %s:~3 %9.9s~2total,~3 %9.9s~2free,~3 %9.9s~2used,~3 %9.9s~2buffers~3\n"
+      "%s %s:~3 %9.9s~2total,~3 %9.9s~2free,~3 %9.9s~2used,~3 %9.9s~2buff/cache~3\n"
-      "%s %s:~3 %9.9s~2total,~3 %9.9s~2free,~3 %9.9s~2used.~3 %9.9s~2cached %s~3\n");
+      "%s %s:~3 %9.9s~2total,~3 %9.9s~2free,~3 %9.9s~2used.~3 %9.9s~2avail %s~3\n");
 
    Uniq_nlstab[INSP_hdrsels_fmt] = _(""
       "Inspection~2 Pause at: pid ~1%d~6 running ~1%s~6 as user ~1%s~6\n"