Messages in this thread |  | | | Date | Thu, 15 Feb 2007 19:46:56 +0100 | | From | bert hubert <> | | Subject | Re: [patch 05/11] syslets: core code |
| |
On Thu, Feb 15, 2007 at 09:42:32AM -0800, Linus Torvalds wrote:
> We know one interface: the current aio_read() one. Nobody really _likes_ [...]
> Others? We don't know yet. And exposing complex interfaces that may not be > the right ones is much *worse* than exposing simple interfaces (that > _also_ may not be the right ones, of course - but simple and
From humble userland, here's two things I'd hope to be able to do, although I admit my needs are rather specialist.
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.
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.
Bert
-- http://www.PowerDNS.com Open source, database driven DNS Software http://netherlabs.nl Open and Closed source services - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
|  |