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Date: Tue, 20 Mar 2007 22:59:10 +0100 From: Zacco <zacco@...hu> To: David Miller <davem@...emloft.net> CC: baruch@...en.org, netdev@...r.kernel.org Subject: Re: many sockets, slow sendto Hi, David Miller wrote: > From: Zacco <zacco@...hu> > Date: Tue, 20 Mar 2007 00:10:19 +0100 > > >> As you recommended, I used oprofile and it turned out that the >> __udp4_lib_lookup function spent most of the time. There is a udp hash >> table and the sockets are sought based on the 7 LSBs of the destination >> port number. So what happened is now quite obvious: I had many thousands >> of sockets, all with the same destination port, thus linked in the same >> slot of this hash table. I tried using different ports and it >> was much faster then. >> > > There isn't much we can do here. I bet your destination address > is unchanging just like your destination ports. > As I'm simulating independent users on one host, each user has a different IP address, but each with the same port. So unlike the port, the address is changing, basically it's a huge A-class range. > UDP apps can and do bind to specific destination addresses and > ports, but the source side is usually wild-carded. > Right, usually it is, but in my case the source addresses are also bound, otherwise the source address would be the primary address of the physical interface; however, I need to simulate users as if they were on separate hosts. > Are both the source address and port fully specified for your > sockets? Maybe we can do something using if that's the case... > You made me curious. :) What do you have in mind? thx: Zacco - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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