Messages in this thread |  | | Date | Mon, 24 Sep 2001 15:20:11 -0700 (PDT) | From | Davide Libenzi <> | Subject | Re: [PATCH] /dev/epoll update ... |
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On 24-Sep-2001 Jamie Lokier wrote: > Davide Libenzi wrote: >> > Well, memory move consists of 2 words: (a) file descriptor; (b) poll >> > state/edge flags. >> >> 2-words * number-of-ready-fds == pretty-high-cache-drain > > Perhaps there is a cache issue, but note it is the number of _new_ ready > fds (since the last sample), not the number currently ready. > >> > That will be completely swamped by the system calls and so on needed to >> > processes each of the file descriptors. I.e. no scalability problem here. >> >> The other issue is that by keeping infos in file* you'll have to scan each fd >> to report the ready ones, that will make the method to fall back in O(n). > > No, that would be silly. You would queue signals exactly as they are > queued now (but collapsing multiple signals per fd into one). > >> Anyway there's a pretty good patch ( http://www.luban.org/GPL/gpl.html ), >> that has been tested here : >> >> http://www.xmailserver.org/linux-patches/nio-improve.html >> >> that implement the signal-per-fd mechanism and it achieves a very good >> scalability too. > > It has the bonus of requiring no userspace changes too. Lovely!
Sure you can avoid the scan, if you pick up one event at a time. To be compared to /dev/epoll you need the signal-per-fd patch plus a method to collect the whole event-set in a single system call ( see perfs ).
- Davide
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