Date: Wed, 22 May 2002 13:21:44 -0400 (EDT) From: Manish Jain <jain@sirius.pc.cis.udel.edu> To: <freebsd-hackers@FreeBSD.ORG> Subject: sendto syscall Message-ID: <20020522122956.P35666-100000@sirius.pc.cis.udel.edu>
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Hello, I am working on a bandwidth measurment tool where I need to send udp packets with fixed interspacing. For this purpose, I am trying to measure the latency of sendto syscall. In one experiment, I set the socket buffer ( both send and receive ) equal to the size of the packet for that experiment ( 512 bytes in that case). Then I do (several) pair of back-to-back sendto and measure their latency using gettimeofday. I repeat the same experiment with a very high value of socket buffer. In first case (socket buffer = pkt size ), I was expecting to see the latecny of second sendto higher relatively to first one since second sendto would block. In the second case , the latency of two sendto should have been of same order. The results of the experiment donot show any trend in the first case nor in the second case. Does anyone have any first thoughts on this ? Does the sendto return after copying the data from user space to kernal space or returns after the packet leaves the interface card ? Thanks, manish http://www.cis.udel.edu/~jain To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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