Messages in this thread | | | From | Eric Dumazet <> | Subject | Re: [patch] epoll reduced (to 1) number of passes over the ready set ... | Date | Tue, 27 Feb 2007 10:15:33 +0100 |
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On Tuesday 27 February 2007 03:32, Davide Libenzi wrote: > Epoll is doing multiple passes over the ready set at the moment, because > of the constraints over the f_op->poll() call. Looking at the code again, > I noticed that we already hold the epoll semaphore in read, and this > (together with other locking conditions that hold while doing an > epoll_wait()) can lead to a smarter way to "ship" events to userspace (in > a single pass). I added more (even) more comments to the code to explain > the conditions why certain operations are safe. > This is a stress application that can be used to test the new code. It > spwans multiple thread and call epoll_wait() and epoll_ctl() from many > threads. Stress tested on my dual Opteron 254 w/out any problems.
Davide,
This is really cool, because the size of epitem would fit now in 128 bytes instead of 192 (on x86_64 platforms). So we also reduce memory usage.
I have one comment :
> */ > - list_for_each(lnk, txlist) { > - epi = list_entry(lnk, struct epitem, txlink); > + for (eventcnt = 0; !list_empty(txlist) && eventcnt < maxevents;) { > + epi = list_entry(txlist->next, struct epitem, rdllink);
Now that we scan the rdllist list once, it may be usefull to use a prefetch() hint.
list_for_each() has one prefetch(pos->next) automatically included, but not your open coded loop.
I suggest adding after epi = list_entry(txlist->next, struct epitem, rdllink); prefetch(epi->rdllink.next);
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