Re: [Libevent-users] How libevent works
On Fri, 5 Jun 2009 18:38:02 -0400 Nick Mathewson wrote: > On Fri, Jun 05, 2009 at 06:31:35PM -0400, Alex wrote: > [...] > > > > Hey, great book! I checked it out of git about an hour ago and have > > been reading it ever since. Since I am decrypting data from the TCP > > stream I might also want to look in to filtering with the > > BEV_NEED_MORE flag as well as the aforementioned watermark. > > > > Okay! You should know that the filtering is a little experimental, > and so you might run into bugs or API warts on it. If you can't make > it do what you want, don't assume that you are the one at fault: let > us know. > Heh, sure thing. > Also, if you're using SSL/TLS, be aware that you can't actually write > a filter for it using the bufferevent_filter API, since sometimes a > TLS read operation can require underlying reads _and_ writes, and the > bufferevent_filter API only works for filters that work as a pure > transform on an input or output stream. > Nope, I am implementing a disgusting proprietary protocol that I did not design. Encryption is built in to the protocol, so a simple transform would suffice (as far as I can predict - I may be wrong). -- Alex ___ Libevent-users mailing list Libevent-users@monkey.org http://monkeymail.org/mailman/listinfo/libevent-users
Re: [Libevent-users] How libevent works
On Fri, Jun 05, 2009 at 06:31:35PM -0400, Alex wrote: [...] > > Hey, great book! I checked it out of git about an hour ago and have > been reading it ever since. Since I am decrypting data from the TCP > stream I might also want to look in to filtering with the BEV_NEED_MORE > flag as well as the aforementioned watermark. > Okay! You should know that the filtering is a little experimental, and so you might run into bugs or API warts on it. If you can't make it do what you want, don't assume that you are the one at fault: let us know. Also, if you're using SSL/TLS, be aware that you can't actually write a filter for it using the bufferevent_filter API, since sometimes a TLS read operation can require underlying reads _and_ writes, and the bufferevent_filter API only works for filters that work as a pure transform on an input or output stream. yrs, -- Nick ___ Libevent-users mailing list Libevent-users@monkey.org http://monkeymail.org/mailman/listinfo/libevent-users
Re: [Libevent-users] How libevent works
On Fri, 5 Jun 2009 18:15:40 -0400 Nick Mathewson wrote: > > - If you set the bufferevent's DEFER_CALLBACKS flag, it doesn't > invoke any of the bufferevent's callbacks until it is done > handling IO for all the other active bufferevents. (So if you set > the flag on all your bufferevents, it does IO on all of them, then > it runs all the appropriate callbacks.) > > The second feature is only available in Libevent 2. I hadn't heard > about a performance boost from clustering the reads on _unrelated_ > sockets, but apparently today is a good day for me learning new > things. > I wanted to use a non-alpha version of libevent, but I just mentally said, "screw it" and decided to use the SVN version. The new features are very nice looking. > > In my case I have to wait until n bytes are recv'd before I can > > begin processing. Therefore it might not be worth it to use > > bufferevents, since I will have to use buffers which are not > > drained. > > It sounds like you want to look at the watermark feature on > bufferevents. You can set a read low-water mark on a bufferevent, and > you won't get a callback until at least that number of bytes have been > read. > > Shameless plug: I'm still making progress in trying to document all > this stuff! You can see the latest draft at > http://www.wangafu.net/~nickm/libevent-book/ > It now covers bufferevents. Please send me corrections where it's > wrong. > Hey, great book! I checked it out of git about an hour ago and have been reading it ever since. Since I am decrypting data from the TCP stream I might also want to look in to filtering with the BEV_NEED_MORE flag as well as the aforementioned watermark. -- Alex ___ Libevent-users mailing list Libevent-users@monkey.org http://monkeymail.org/mailman/listinfo/libevent-users
Re: [Libevent-users] How libevent works
On Fri, Jun 05, 2009 at 03:17:00PM -0400, Alex wrote: > Hey there. When working with bufferevents, in what order does libevent > execute callbacks? Does it fill all the buffers first and then call the > CBs, or does it fill a buffer and call its corresponding CB, one at a > time? > > From what I understand, it is more efficient to recv and send on all > available sockets all at once rather than recv, process, recv, > process, etc. By default, the bufferevent tries to read as much data as it can, and it invoke the read callback after it has done so. You can change this behavior in a few ways, including: - If you set a low-watermark for reading on that bufferevent, it doesn't invoke the callback until a given number of bytes are available. - If you set the bufferevent's DEFER_CALLBACKS flag, it doesn't invoke any of the bufferevent's callbacks until it is done handling IO for all the other active bufferevents. (So if you set the flag on all your bufferevents, it does IO on all of them, then it runs all the appropriate callbacks.) The second feature is only available in Libevent 2. I hadn't heard about a performance boost from clustering the reads on _unrelated_ sockets, but apparently today is a good day for me learning new things. > In my case I have to wait until n bytes are recv'd before I can begin > processing. Therefore it might not be worth it to use bufferevents, > since I will have to use buffers which are not drained. It sounds like you want to look at the watermark feature on bufferevents. You can set a read low-water mark on a bufferevent, and you won't get a callback until at least that number of bytes have been read. Shameless plug: I'm still making progress in trying to document all this stuff! You can see the latest draft at http://www.wangafu.net/~nickm/libevent-book/ It now covers bufferevents. Please send me corrections where it's wrong. yrs, -- Nick ___ Libevent-users mailing list Libevent-users@monkey.org http://monkeymail.org/mailman/listinfo/libevent-users
[Libevent-users] How libevent works
Hey there. When working with bufferevents, in what order does libevent execute callbacks? Does it fill all the buffers first and then call the CBs, or does it fill a buffer and call its corresponding CB, one at a time? From what I understand, it is more efficient to recv and send on all available sockets all at once rather than recv, process, recv, process, etc. In my case I have to wait until n bytes are recv'd before I can begin processing. Therefore it might not be worth it to use bufferevents, since I will have to use buffers which are not drained. -- Alex ___ Libevent-users mailing list Libevent-users@monkey.org http://monkeymail.org/mailman/listinfo/libevent-users
