Lua memory leak in C process -

i have c program running lua.

although try use lua_gc() , control memory usage of lua, c process memory usage still high. c process uses on 150mb memory though lua uses 4mb memory.

i try use l_alloc() function track lua memory allocation, result same memory usage lua told calling lua_gc(lua_gccount) , lua_gc(lua_gccountb).

after calling lua_close() close lua environment, process memory down , looks fine. therefore, think 'lost memory' still controlled lua not c program.

here sample c code. creates lua environment, calls lua function purge data , check memory usage.

int main() {     int rc;     uint64_t gc_mem_usage;      lua_state* lua = lual_newstate();     lual_openlibs(lua);      lua_gc(lua, lua_gcstop, 0);     lual_dofile(lua, "test.lua");      gc_mem_usage = ((uint64_t)lua_gc(lua, lua_gccount, 0) << 10) + lua_gc(lua, lua_gccountb, 0);     printf("lua mem usage: [%" priu64 "] bytes\n", gc_mem_usage);      lua_getglobal(lua, "command_handler");     lua_pushstring(lua, "cc");     rc = lua_pcall(lua, 1, 0, 0);     if (rc != 0 ) {         printf("function error\n");         return;     }      lua_settop(lua, 0);      // full gc     lua_gc(lua, lua_gccollect, 0);     lua_gc(lua, lua_gccollect, 0); // don't know why has different result calling full gc twice     sleep(1);      printf("-------------after gc ----------------------\n");     gc_mem_usage = ((uint64_t)lua_gc(lua, lua_gccount, 0) << 10) + lua_gc(lua, lua_gccountb, 0);     printf("lua mem usage: [%" priu64 "] bytes\n", gc_mem_usage);      // infinite-loop     while(1); } 

lua sample code:

local abc = {}  function command_handler(cmd)     if (cmd == "cc")         abc = {}     end end  =0, 2000000     abc[i] = "abc" .. .. "def" end 

output:

lua mem usage: [204913817] bytes -------------after gc ---------------------- lua mem usage: [4219342] bytes 

the output told me lua memory usage down after gc, memory usage of c process still high (193.7mb) checking atop continuously.

 pid minflt majflt      vstext  vsize  rsize  vgrow  rgrow  mem cmd     1/1 4622      1      0          3k 193.7m 183.9m     0k     4k  18% a.out 

is there solution reduce c process memory usage?

my environment lua 5.1.4 running in ubuntu/centos.

lua faithfully frees unreachable objects calling supplied deallocation function (by default realloc(block, 0)). looks libc allocator struggling return unused memory, possibly due high fragmentation. looking @ strace output (i've got same numbers lua 5.1.4 on 64-bit debian 6), c runtime chooses allocate using brk small increments, no deallocation (calling brk lower value) follows. however, if insert malloc_trim(m_top_pad) before entering infinite loop, you'll see in top output resident size drops drastically ~5m , strace reveals data segment indeed trimmed brk. using custom allocator (e.g. pool-based) or tuning malloc parameters in situation.