debate on 700 threads vs asynchronous code
Quoted 11 lines · Lee Chin
Quoted 9 lines · Larry McVoy
Quoted 5 lines
Now, to cater to 700 clients, I can
a) launch 700 threads that each block on I/O to disk and to the client (in reading and writing on the socket) OR
b) Write an asycnhrounous system with only 2 or three threads where I manage the
connections and stack (via setcontext swapcontext etc), which is programatically a little harder Which way will yeild me better performance, considerng both approaches are implemented optimally?If this is a serious question, an async system will by definition do better. You have either 700 stacks screwing up the data cache or 2-3 stacks nicely fitting in the data cache. Ditto for instruction cache, etc.
Quoted 5 lines
Thanks for the rpely... my question was more so, with setcontext and swapcontext, I will still be messing with the data cache right?
In otherwords, as long as I have an async system with out setcontext, I know I am good... but with it, havent I degraded to a threaded environment?
I suspect Linux's implementation of asynch I/O isn't able to handle sockets yet. Thus the choice is between nonblocking I/O and blocking I/O.
Nonblocking I/O is totally the way to go if you have full control over your source code and want the maximal performance in userspace. The best way to get good performance with nonblocking I/O in Linux is to use the sys_epoll system call; it's part of the 2.5 kernel, but a backport to 2.4 is available.
See http://www.kegel.com/c10k.html for an overview of the issue and some links.
- Dan
Signature · 3 lines
Dan Kegel http://www.kegel.com http://counter.li.org/cgi-bin/runscript/display-person.cgi?user=78045