William A. Rowe, Jr. wrote:
At 10:15 AM 8/3/2002, Rob Saccoccio wrote:
Its not clear to me which poll API should be used when. Apache uses the
deprecated API. Some thoughts on the subject should probably be put in
poll.h and Apache updated.
I'm as stumped as you. FWIW, both should work. It makes no difference
right now,
If you're polling on a single file/socket descriptor,
both APIs do about the same processing on the first poll
(mostly just copying from the apr_pollfd_t to the OS's
pollfd struct). If you expect to have to call poll on
that same descriptor repeatedly, the apr_pollset API
is more efficient than the apr_poll API, because the
pollset API doesn't have to repeat this setup work on
subsequent requests. On the other hand, to take
advantage of this property of the apr_pollset API,
you need to be able to keep track of the pollset
object between calls. In situations where it's
prohibitively complex for the app to maintain a pollset
object, the apr_poll API is simpler to use.
For larger numbers of descriptors, the apr_pollset
API scales better than apr_poll, as the pollset code
doesn't need to do an O(n) copy on each poll call.
Thus my rule of thumb for choosing between the poll
APIs is:
if (very small number of file descriptors) {
if ((poll will be repeated multiple times) &&
(application can keep track of a pollset object)) {
use apr_pollset API;
}
else {
use apr_poll API;
}
}
else {
use apr_pollset API;
}
but will when Brian implements /dev/poll [or /dev/epoll] and I attack
WSAAsyncSelect, both of which require the accessor-based api to be easily
reusable [performantly] from poll to poll.
Definitely.
--Brian
