What is the concept of "Lost RAM" that appears in Memories Dumpsys?

Question

As I mentioned, Lost RAM appears in Dumpsys meminfo.

• What is the concept of "Lost RAM" that appears in Duncys meminfo?
• What is its significance in Kitkat. How can it be returned and used?

Dumpsys example showing "Lost memory".

Total RAM: 998096 kB
 Free RAM: 574945 kB (145869 cached pss + 393200 cached + 35876 free)

 Used RAM: 392334 kB (240642 used pss + 107196 buffers + 3856 shmem + 40640 slab)

 Lost RAM: 30817 kB

   Tuning: 64 (large 384), oom 122880 kB, restore limit 40960 kB (high-end-gfx)

Answer 1

On my system, they are mainly called ION (which replaces pmem). If debug ion is enabled in your kernel, you can calculate the use of ION with this script:

adb shell cat /d/ion/heaps/system|perl -ne 'chomp; if (m/pages in.*pool = (\d+) total/) {$x += $1;} if (m/^\s+total\s+(\d+)$/) {$y += $1} END {printf "use: %d kb, cache: %d kb; total: %d kb", $y/1024, $x/1024, ($x + $y)/1024}'

, , , , .

, , .awk script (dmsys meminfo meminfo , , ), ION:

#!/usr/bin/awk

BEGIN {
    types["MemTotal"] = 1;
    types["Pss"] = 1;
    types["MemFree"] = 1;
    types["Cached"] = 1;
    types["Buffers"] = 1;
    types["Shmem"] = 1;
    types["Slab"] = 1;
}


## start code-generator "^\\s *#"
#echo
# for x in Pss MemTotal MemFree Cached Buffers Shmem Slab; do
#     cat << EOF
#/$x: / {
#     hash["$x"] += \$2;
# next
#}
#
#EOF
# done
## end code-generator
## start generated code

/Pss: / {
    hash["Pss"] += $2;
    next
 }

 /MemTotal: / {
     hash["MemTotal"] += $2;
     next
 }

 /MemFree: / {
     hash["MemFree"] += $2;
     next
 }

 /Cached: / {
     hash["Cached"] += $2;
     next
 }

 /Buffers: / {
     hash["Buffers"] += $2;
     next
 }

 /Shmem: / {
     hash["Shmem"] += $2;
     next
 }

 /Slab: / {
     hash["Slab"] += $2;
     next
 }


## end generated code

END {
    lost =  0;
    for (type in types) {
        if (type == "MemTotal") {
            lost += hash[type];
        } else {
            lost -= hash[type];
        }
    }
    print "lost: " lost " kB\n";
}

, adb shell sh -c 'echo 3 > /proc/sys/vm/drop_caches', .