On Thu, Feb 15, 2007 at 07:46:56PM +0100, bert hubert ([EMAIL PROTECTED]) wrote: > 1) batch, and wait for, with proper error reporting: > socket(); > [ setsockopt(); ] > bind(); > connect(); > gettimeofday(); // doesn't *always* happen > send(); > recv(); > gettimeofday(); // doesn't *always* happen > > I go through this sequence for each outgoing powerdns UDP query > because I need a new random source port for each query, and I > connect because I care about errrors. Linux does not give me random > source ports for UDP sockets.
What about a setsockopt or just random port selection patch? :) > When async, I can probably just drop the setsockopt (for > nonblocking). I already batch the gettimeofday to 'once per epoll > return', but quite often this is once per packet. > > 2) On the client facing side (port 53), I'd very much hope for a way to > do 'recvv' on datagram sockets, so I can retrieve a whole bunch of > UDP datagrams with only one kernel transition. > > This would mean that I batch up either 10 calls to recv(), or one > 'atom' of 10 recv's. > > Both 1 and 2 are currently limiting factors when I enter the 100kqps domain > of name serving. This doesn't mean the rest of my code is as tight as it > could be, but I spend a significant portion of time in the kernel even at > moderate (10kqps effective) loads, even though I already use epoll. A busy > PowerDNS recursor typically spends 25% to 50% of its time on 'sy' load. > > This might be due to my use of get/set/swap/makecontext though. It is only about one syscall in get and set/swap context, btw, so it should not be a main factor, doesn't it? As an advertisement note, but if you have a lot of network events per epoll read try to use kevent - its socket notifications do not require additional traverse of the list of ready events as in poll usage. > Bert > > -- > http://www.PowerDNS.com Open source, database driven DNS Software > http://netherlabs.nl Open and Closed source services -- Evgeniy Polyakov - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
