Hello folks,

I noticed while stracing a process that sock.setblocking() calls always result in pairs of fcntl() calls on Linux. Checking 2.6.8, 2.7.3, and 3.3.0 Modules/socketmodule.c, the code seems to use the following (unless I have missed something):

delay_flag = fcntl(s->sock_fd, F_GETFL, 0);

if (block)

delay_flag &= (~O_NONBLOCK);

else

delay_flag |= O_NONBLOCK;

fcntl(s->sock_fd, F_SETFL, delay_flag);

Perhaps a check to see the flags changed might be worth making?

int orig_delay_flag = fcntl(s->sock_fd, F_GETFL, 0);

if (block)

delay_flag = orig_delay_flag & (~O_NONBLOCK);

else

delay_flag = orig_delay_flag | O_NONBLOCK;

if (delay_flag != orig_delay_flag)

fcntl(s->sock_fd, F_SETFL, delay_flag);

OpenStack Swift using the Eventlet module, which sets the accepted socket non-blocking, resulting in twice the number of fcntl() calls. Not a killer on performance, but it seems simple enough to save a system call here.

Thanks for your consideration,

-peter