[PHP] PHP Memory Allocation (checked via TOP)
Hi, I have written a simple test program to see how php allocates memory. Test code allocates ~10 Meg of RAM in an array within a loop till it runs out of memory as: $str = rand(65, 95) . rand(65, 95) . rand(65, 95) . rand(65, 95) . rand(65, 95); $aa[] = str_repeat($str, 200); What I don't understand here is, for every 10 Meg memory it allocates, mem usage goes up about 19 Megs when I look at this via top. Basically, it allocates from physical memory in the beginning, starts using swap when it is out of RES/Physical memory, which makes me assume that garbage collection should kick in for temporary string creations, and each new allocation increases the allocated memory size by 19 Megs. Any idea why this is happening, and why do you think memory allocation is so expensive in PHP? Thanks.. Results of TOP: PID USER PR NI VIRT RES SHR S %CPU %MEMTIME+ COMMAND 21843 apache17 0 19292 5232 3832 S 0.0 0.5 0:00.04 php 21843 apache16 0 38824 24m 3908 S 0.0 2.4 0:00.10 php 21843 apache15 0 58356 43m 3912 S 0.0 4.3 0:00.17 php 21843 apache16 0 77888 62m 3912 S 0.0 6.2 0:00.22 php 21843 apache15 0 97420 81m 3912 S 0.0 8.1 0:00.29 php 21843 apache15 0 114m 100m 3912 S 0.0 9.9 0:00.35 php Results of free -m: total used free sharedbuffers cached Mem: 1011138872 0 2 58 Swap: 2008388 1619 Mem: 1011158852 0 2 58 Swap: 2008388 1619 Mem: 1011177833 0 2 58 Swap: 2008388 1619 Mem: 1011196814 0 2 58 Swap: 2008388 1619 Mem: 1011216795 0 2 58 Swap: 2008388 1619 Mem: 1011234776 0 2 58 Swap: 2008388 1619 -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP] PHP Memory Allocation (checked via TOP)
Cabbar Duzayak wrote: Hi, I have written a simple test program to see how php allocates memory. Test code allocates ~10 Meg of RAM in an array within a loop till it runs out of memory as: $str = rand(65, 95) . rand(65, 95) . rand(65, 95) . rand(65, 95) . rand(65, 95); $aa[] = str_repeat($str, 200); What I don't understand here is, for every 10 Meg memory it allocates, mem usage goes up about 19 Megs when I look at this via top. Just looked over this really quickly, so I might have missed something, but it seems to me that you're allocating almost 20 megs... your $str is 10 bytes long (plus terminator and PHP overhead, whatever that turns out to be...), and you're repeating it two million times. 10 bytes times 2 million is 20 million bytes. 20 000 000 divided by (1024*1024) is 19.07 - it seems to me that you're allocating 19.07 megs, and top is showing you that it's allocating 19 megs...? Seems about right. jon -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP] PHP Memory Allocation (checked via TOP)
$str is 10 bytes then you repeat it 200 times That gives you 2000 bytes. That's 20M not 10M -Rasmus Cabbar Duzayak wrote: Hi, I have written a simple test program to see how php allocates memory. Test code allocates ~10 Meg of RAM in an array within a loop till it runs out of memory as: $str = rand(65, 95) . rand(65, 95) . rand(65, 95) . rand(65, 95) . rand(65, 95); $aa[] = str_repeat($str, 200); What I don't understand here is, for every 10 Meg memory it allocates, mem usage goes up about 19 Megs when I look at this via top. Basically, it allocates from physical memory in the beginning, starts using swap when it is out of RES/Physical memory, which makes me assume that garbage collection should kick in for temporary string creations, and each new allocation increases the allocated memory size by 19 Megs. Any idea why this is happening, and why do you think memory allocation is so expensive in PHP? Thanks.. Results of TOP: PID USER PR NI VIRT RES SHR S %CPU %MEMTIME+ COMMAND 21843 apache17 0 19292 5232 3832 S 0.0 0.5 0:00.04 php 21843 apache16 0 38824 24m 3908 S 0.0 2.4 0:00.10 php 21843 apache15 0 58356 43m 3912 S 0.0 4.3 0:00.17 php 21843 apache16 0 77888 62m 3912 S 0.0 6.2 0:00.22 php 21843 apache15 0 97420 81m 3912 S 0.0 8.1 0:00.29 php 21843 apache15 0 114m 100m 3912 S 0.0 9.9 0:00.35 php Results of free -m: total used free sharedbuffers cached Mem: 1011138872 0 2 58 Swap: 2008388 1619 Mem: 1011158852 0 2 58 Swap: 2008388 1619 Mem: 1011177833 0 2 58 Swap: 2008388 1619 Mem: 1011196814 0 2 58 Swap: 2008388 1619 Mem: 1011216795 0 2 58 Swap: 2008388 1619 Mem: 1011234776 0 2 58 Swap: 2008388 1619 -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
