centos + php leak memory, but where?

Question

I have a big php cronjob that run every 20minutes. After each execution the RAM memory used by the virtual server increase and not properly free once the script is terminated!

But why? The memory isn't cached

 total used free shared buffers cached Mem: 2048 1948 99 0 0 88 -/+ buffers/cache: 1859 188 Swap: 0 0 0 

The script make some curl/multi_curl and update the Mysql DB.

There is a way to debug the script seeing all the variable and the memory usage over time? or simple the ones not released at the end...

Answer 1

The memory should be freed when a program exits (regardless if the program freed it or not). For example.

[kbrandt@ny-kbrandt01: ~] cat eat_mem.c #include <stdlib.h> #include <string.h> #include <unistd.h> int main() { #1 GByte const int m = 1024*1024*1024; #Allocate a gig void *p = (int*)malloc(m); #Write a Gigs worth of zeros to that gig memset(p,0,m); sleep(10); #In theory I should free(p) here (heh... heh... I said "free p", get it?) return 0; } [kbrandt@ny-kbrandt01: ~] gcc eat_mem.c; ./a.out &; sleep 1; free -m;sleep 10; free -m [1] 10666 total used free shared buffers cached Mem: 7872 1848 6023 0 143 431 -/+ buffers/cache: 1273 6599 Swap: 30467 0 30467 [1] + done ./a.out total used free shared buffers cached Mem: 7872 823 7049 0 143 431 -/+ buffers/cache: 247 7624 Swap: 30467 0 30467 

So assuming your script run the by the cron job exits, that would not be the issue. So you need to see which program is growing in memory. You can just watch this using top (You can sort by resident memory size by pressing F (capital) and then q for RES in top) and see what program grows.

My guess is that it is going to be MySQL, because whatever your script does, it does stuff in SQL and SQL ends up using more memory. This probably actually isn't a problem if I had to guess, MySQL will take the memory it can get and use it wisely most of the time.