free: add 'available' memory if provided by the kernel

Show estimated available memory if this is provided by the
kernel. See [1] for the full story.

 [1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=34e431b0ae398fc54ea69ff85ec700722c9da773

function                                             old     new   delta
free_main                                            537     633     +96
parse_cached_kb                                       85       -     -85
------------------------------------------------------------------------------
(add/remove: 0/1 grow/shrink: 1/0 up/down: 96/-85)             Total: 11 bytes

Signed-off-by: Guillermo Rodriguez <guille.rodriguez@gmail.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

diff --git a/procps/free.c b/procps/free.c
index 48139c4a3d6d3d2d7c8d41b24cc1e14a2e808652..e41601e08ee5bc64a67b9e091f5b2b80906f525d 100644 (file)
--- a/procps/free.c
+++ b/procps/free.c
@@ -53,21 +53,27 @@ static unsigned long long scale(struct globals *g, unsigned long d)
 }
 
 /* NOINLINE reduces main() stack usage, which makes code smaller (on x86 at least) */
-static NOINLINE unsigned long parse_cached_kb(void)
+static NOINLINE unsigned int parse_meminfo(unsigned long *cached_kb, unsigned long *available_kb)
 {
        char buf[60]; /* actual lines we expect are ~30 chars or less */
        FILE *fp;
-       unsigned long cached = 0;
+       int seen_cached_and_available;
 
        fp = xfopen_for_read("/proc/meminfo");
-       while (fgets(buf, sizeof(buf), fp) != NULL) {
-               if (sscanf(buf, "Cached: %lu %*s\n", &cached) == 1)
-                       break;
+       *cached_kb = *available_kb = 0;
+       seen_cached_and_available = 2;
+       while (fgets(buf, sizeof(buf), fp)) {
+               if (sscanf(buf, "Cached: %lu %*s\n", cached_kb) == 1)
+                       if (--seen_cached_and_available == 0)
+                               break;
+               if (sscanf(buf, "MemAvailable: %lu %*s\n", available_kb) == 1)
+                       if (--seen_cached_and_available == 0)
+                               break;
        }
        /* Have to close because of NOFORK */
        fclose(fp);
 
-       return cached;
+       return seen_cached_and_available == 0;
 }
 
 int free_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
@@ -75,7 +81,9 @@ int free_main(int argc UNUSED_PARAM, char **argv IF_NOT_DESKTOP(UNUSED_PARAM))
 {
        struct globals G;
        struct sysinfo info;
-       unsigned long long cached;
+       unsigned long long cached, cached_plus_free, available;
+       unsigned long cached_kb, available_kb;
+       int seen_available;
 
 #if ENABLE_DESKTOP
        G.unit_steps = 10;
@@ -98,41 +106,46 @@ int free_main(int argc UNUSED_PARAM, char **argv IF_NOT_DESKTOP(UNUSED_PARAM))
                }
        }
 #endif
-       printf("       %11s%11s%11s%11s%11s%11s\n"
+       printf("       %12s%12s%12s%12s%12s%12s\n"
        "Mem:   ",
                "total",
                "used",
                "free",
-               "shared", "buffers", "cached" /* swap and total don't have these columns */
+               "shared", "buff/cache", "available" /* swap and total don't have these columns */
        );
 
        sysinfo(&info);
        /* Kernels prior to 2.4.x will return info.mem_unit==0, so cope... */
        G.mem_unit = (info.mem_unit ? info.mem_unit : 1);
-       /* Extract cached from /proc/meminfo and convert to mem_units */
-       cached = ((unsigned long long) parse_cached_kb() * 1024) / G.mem_unit;
+       /* Extract cached and memavailable from /proc/meminfo and convert to mem_units */
+       seen_available = parse_meminfo(&cached_kb, &available_kb);
+       available = ((unsigned long long) available_kb * 1024) / G.mem_unit;
+       cached = ((unsigned long long) cached_kb * 1024) / G.mem_unit;
+       cached += info.bufferram;
+       cached_plus_free = cached + info.freeram;
 
-#define FIELDS_6 "%11llu%11llu%11llu%11llu%11llu%11llu\n"
+#define FIELDS_6 "%12llu%12llu%12llu%12llu%12llu%12llu\n"
 #define FIELDS_3 (FIELDS_6 + 3*6)
 #define FIELDS_2 (FIELDS_6 + 4*6)
 
        printf(FIELDS_6,
                scale(&G, info.totalram),                //total
-               scale(&G, info.totalram - info.freeram), //used
+               scale(&G, info.totalram - cached_plus_free), //used
                scale(&G, info.freeram),                 //free
                scale(&G, info.sharedram),               //shared
-               scale(&G, info.bufferram),               //buffers
-               scale(&G, cached)                        //cached
+               scale(&G, cached),                       //buff/cache
+               scale(&G, available)                     //available
        );
-       /* Show alternate, more meaningful busy/free numbers by counting
+       /* On kernels < 3.14, MemAvailable is not provided.
+        * Show alternate, more meaningful busy/free numbers by counting
         * buffer cache as free memory. */
-       printf("-/+ buffers/cache:");
-       cached += info.freeram;
-       cached += info.bufferram;
-       printf(FIELDS_2,
-               scale(&G, info.totalram - cached), //used
-               scale(&G, cached)                  //free
-       );
+       if (!seen_available) {
+               printf("-/+ buffers/cache: ");
+               printf(FIELDS_2,
+                       scale(&G, info.totalram - cached_plus_free), //used
+                       scale(&G, cached_plus_free)                  //free
+               );
+       }
 #if BB_MMU
        printf("Swap:  ");
        printf(FIELDS_3,