On 2008-Jul-15 16:09:17 -0700, Bakul Shah <[EMAIL PROTECTED]> wrote: >IIRC, when poll() returns n, you only look at the first n >values in the pollfd array so it is a win when you expect a >very small number of fds to be ready. In the select case you >have to test the bit array until you see the last ready fd.
No. Both poll(2) and select(2) return the number of FDs ready for I/O. You need to scan the pollfd or fd_set array until you find that many FDs ready. poll(2) is a win if you only need to test a small number of FDs compared to the number of FDs that the process has open. In the case of bind, you have a large number of FDs to test, of which you are only expecting a very small number to be ready - if you don't treat fd_set as opaque, select(2) allows you to quickly skip large (roughly wordsize) chunks of un-interesting FDs. Note that, based on sys_generic.c in 7.x and -CURRENT, poll(2) is limited to checking FD_SETSIZE descriptors, whilst select(2) has no upper limit. -- Peter Jeremy Please excuse any delays as the result of my ISP's inability to implement an MTA that is either RFC2821-compliant or matches their claimed behaviour.
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