On Mon, 2009-05-04 at 19:41 -0400, Martin Peach wrote:
Roman Haefeli wrote:
On Fri, 2009-05-01 at 18:48 -0400, Martin Peach wrote:
Roman Haefeli wrote:
On Fri, 2009-05-01 at 09:16 -0400, Martin Peach wrote:
Roman Haefeli wrote:
On Thu, 2009-04-30 at 10:17 -0400, Martin Peach wrote: > Roman Haefeli wrote: >> i ve been testing the new netpd-server based on the new >> [tcpserver]/[tcsocketserver FUDI] now for a while and definitely could >> solve some problems, but some new ones were introduced. >> >> i found, that the most recent version of [tcpserver] peforms quite bad >> cpu-wise. this has some side-effects. in netpd, when a certain number of >> users are logged in (let's say 16), it can happen, that the traffic of >> those clients makes the netpd-server use more than the available >> cpu-time. i made some tests and checked, if all messages come through >> and if messages delivered by the server are still intact. under normal >> circumstances, there is no problem at all. but under heavy load, when >> the pd process is demanding more than available cpu time, some messages >> are corrupted or lost completely; in the worst case the pd process >> segfaults, at the moment of a client connecting or disconnecting. i >> guess, this is due to some buffer under- or overrun between pd and the >> tcp stack, but i don't really know. > Hi Roman, > Did you try using the new [timeout( message? The latest version of > tcpserver defaults to a 1ms timeout, so if you have a bunch if > disconnected clients, Pd will hang for 1ms each, which will quickly add > up to more than the audio block time and then Pd will start thrashing > and eventually die or become comatose, as it were. no, i haven't tried this parameter yet. but i sure will do and report back, when i can tell more about how it behaves.
i haven't fully understood, what it does and what it can be used for. could you elaborate that a bit more? yet it sounds a bit strange to me, that i need to tweak a networking object with a time value for correct operation.
When you send some message through tcpserver, the send routne first checks to see if it can be sent. The call to do this is a function known as "select", which has a timeout parameter. The select call returns as soon as the socket is available or the timeout expires, whichever comes first. If the socket is blocked, select would never return if there was no timeout. So I gave the call a default 1ms timeout.
ok. i think, i understand. thanks for the explanation.
This could all be done using threads as well but I just don't know when I'll have time to do it.
no hurry. it's not the case, that i know, that threading would help for the issues, i am experiencing. i just wanted to have my troubles reported. and i think, i read somewhere about server implementations, that they often use a separate thread for each socket.
I still don't see that it would solve your problem anyway, if your application insists on sending to disconnected clients, you would have lots of threads sitting around, and still get no feedback about the connection.
the only feedback needed: was something actually sent or not? if you (or the patch) _know_, that messages are not received by the other end, then you (the patch) can handle the situation somehow. anyway, that is the part that seems to be already working. by using the current [tcpserver], you notice, if the other end vanished or is still listening. the problems i currently encounter are coming from the fact, that the performance of the new version is probably 20 times worse than the version included in current stable pd-extended. for me its a problem, since with a certain sane number of clients connected (let's say 16), it already overloads the cpu of a 1.7GHz pentium m processor. why the big difference to the previous version?
If you set the sending timeout to zero (by sending [timeout 0( message to [tcpserver] )then the performance should be the same as the older version. AFAIK that's all I changed. Did you try that yet? If not, something else is causing the slowdown. If it works better, maybe set the timeout to 10 instead of 1000.
there is no difference in performance, no matter what value i use for 'timeout'. on my box, sending the message (in byte representation) from the benchmark test 1000 times takes ~90ms for [tcpserver]. the same (in ascii presentation) sent with [netserver] takes around 8ms. the only difference i can see with lower (< 10us) timeout value is, that messages on the receiving side (client) are messed up, completely lost, partially cut or concatenated together. on my box, the new [tcpserver] with 'timeout' set to 0 performs much worse than the old version with the buffer overrun problem.
Maybe just calling select slows everything down then. It seems to be a trade-off between speed and reliability. You should really send udp packets, then nothing hangs if the other end doesn't receive them. You could still have a low-bandwidth tcp connection open to test the connection.
udp is no option for me (see previous mails). i really do need a working netpd-server and the good thing is, that the server doesn't necessarily needs to be written in pd. i think, i'll try the python road. i know a little python, whereas c is definitely too low level for me, altough it probably might be much more performant for what i want.
besides my situation, [tcpserver] generally isn't yet fully usuable under real world conditions, although it has been improved a lot ( thanks for all your efforts!!! ). for serious use, i think, the performance issue is a real problem. but i also encountered other troubles.
in particular, there are certain situations, where the pd process running the [tcpserver] based netpd-server segfaults. this happens usually, when: a) there is some net traffic going on, and b) a client connects or disconnects. i wasn't able to track the problem down, so i am not really sure, where the problem comes from, but the fact, that it only happens on connects or disconnects lets me assume, that it is somehow related to [tcpserver]. now i wonder: is it safe at any time to send whatever message to [tcpserver]? could it be, that [tcpserver] is 'confused', when a certain client disconnects, while [tcpserver] is sending data to this particular client?
this problem doesn't exist with the [netserver] based netpd-server actually this patch/external combo never ever segfaulted, as far as i remember, the only problems were a hanging pd process due to full buffer.
have you tested on windows only? i haven't tried windows yet. how did you test?
I didn't test for speed at all, I just checked that it worked on WinXP and Debian.
i posted a benchmark patch in first mail of this thread, if you're interested.
roman
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