Messages in this thread | | | Date | Tue, 27 Feb 2007 08:03:53 -0800 (PST) | From | Davide Libenzi <> | Subject | Re: [patch] epoll reduced (to 1) number of passes over the ready set ... |
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On Tue, 27 Feb 2007, Eric Dumazet wrote:
> 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.
Yeah, I forgot to mention that I removed the txlink member.
> 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);
Will do in the next version, thx!
- Davide
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