Date: Sat, 20 Mar 1999 23:30:42 -0800 (PST) From: Matthew Dillon <dillon@apollo.backplane.com> To: Bill Paul <wpaul@skynet.ctr.columbia.edu> Cc: julian@whistle.com (Julian Elischer), hackers@freebsd.org Subject: Re: Gigabit ethernet revisited Message-ID: <199903210730.XAA09427@apollo.backplane.com> References: <199903210718.CAA08119@skynet.ctr.columbia.edu>
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:So, how long after the process is marked runable does the scheduler
:actually transfer control to the process so that it can handle the
:received data? Can the process be prevented from running if there are
:too many interrupts from the NIC? Is there some way to make the scheduler
:run the process more often (I tried using nice -20 on the receving
:instance of ttcp; that didn't seem to make a difference)? Has anybody
:else actually tried to receive data at 600 to 800Mbps speeds on FreeBSD
:and done it reliably? (Note: I mean actually transmitting UDP packets at,
:say 80MB/sec and actually receiving _all_ of the transmitted packets on
:the other side, in the application, at the same speed. No fudging.)
:Transmit speed doesn't seem to be an issue here, but somehow I get the
:feeling that the kernel is sabotaging itself on receive.
:
:-Bill
You need to do the test I suggested sinking the packets into the
bit bucket with ipfw.
You also need to do a cpu loading test - graph the cpu utilization
as displayed by vmstat or 'systat -vm 1' verses the packet load,
both going into the bit bucket, or being read by a process.
If there is any cpu available, runnable processes will run no matter
what the cpu load.
-Matt
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