Re: Performance of while(true) loop

On Wed, Sep 9, 2009 at 10:32 PM, APseudoUtopia <apseudoutopia@gmail.com> wrote: > Hey list, > > I have a php cli script that listens on a UDP socket and, when data is > sent to the socket, the script inserts it into a database. I'm using > the real BSD socket functions, not fsock. > > The script runs socket_create(), then socket_bind(). Then it starts a > while(TRUE) loop. Within the loop, it runs socket_recvfrom(). I have > it running 24/7 inside a screen window. > > I'm curious as to the cpu/memory/etc usage of a while(true) loop. The > top command shows that the process is in the sbwait state (the > OS is > FreeBSD). I'm contemplating adding a usleep or even a sleep inside to > loop. Would this be beneficial? I'm not too sure of how the internals > of PHP work in terms of loops and such. > > Thanks. > > -- > PHP General Mailing List (http://www.php.net/) > To unsubscribe, visit: http://www.php.net/unsub.php > > Is your socket blocking? If so, what's the timeout? while(true) { //wait for socket timeout } is the same as: while(true) { //read nothing from socket and sleep } Without the usleep(), the loop is going to loop as fast as your CPU will let it - meaning 100% CPU usage, all the time, at least in linux, although I'm pretty sure BSD would behave the same. As far as I'm aware, sockets in PHP behave almost identically to the way that they behave in C. I had an asynchronous TCP server written with the socket_* functions and noticed that the while(true) loop used 100% of the CPU because of the nonblocking sockets in use, but a usleep() solved that quite easily. Using blocking sockets with socket_select and a sane timeout relieved the high CPU usage as well.