Date: Tue, 24 Oct 1995 18:43:30 +1000 From: Bruce Evans <bde@zeta.org.au> To: dennis@etinc.com, terry@lambert.org Cc: hackers@FreeBSD.ORG Subject: Re: Bragging rights.. Message-ID: <199510240843.SAA06640@godzilla.zeta.org.au>
next in thread | raw e-mail | index | archive | help
>> I really can't believe you guys are bragging about the widespread >> utilization of >> souped-up async. You still don't get the fact that you're losing several >> hundred dollars >> worth of machine (which brings the cost in-line with sync) to save a few >> hundred on >> cards for a less-efficient solution. How much less efficient? For logins, even a local ethernet is only a few times more efficient than 115200 bps async through a 16450. This is mostly because the pty implementation is poor. Actual measurements: $ # Throughput: $ sh -c "od /kernel | head -10000 | wc" 649244 $login-through-sio0 time sh -c "od /kernel | head -10000" ... 57.51 8.04 2.07 $ expr 64924400 / 5751 11289 # bytes/sec $login-through-ethernet time sh -c "od /kernel | head -10000" 17.49 real 6.61 user 2.17 sys $ expr 64924400 / 1749 37120 # bytes/second $ # Ethernet is only 3 times faster than async serial :-(. $ # Server is 486DX/33 $ # `count' is a cpu hog process that does nothing atoi(argv[1]) times $idle-server time count 50000000 7.71 real 7.61 user 0.03 sys $ # Client is 486DX2/66 $idle-client time count 100000000 7.58 real 7.55 user 0.91 sys $ # Server's UART is 16450. $server-writing-infinite-od-output-to-sio0 time count 50000000 11.08 real 8.90 user 0.03 sys $ expr \( 1108 - 771 \) \* 1000 / 1108 304 # overhead 30.4% $ # Other measurements show that serial write overhead on this system is 19.5% $ # Client's UART is 16550. $client-reading-infinite-od-output-from-sio0 time count 100000000 8.79 real 7.88 user 0.03 sys $ expr \( 879 - 758 \) \* 1000 / 879 137 # overhead 13.7% $ # Other measurements show that serial read overhead on this system is 6.3% $ # Server's ethernet is WD8013EBT. $server-writing-infinite-od-output-to-ethernet time count 50000000 17.39 real 7.60 user 0.03 sys $ expr \( 1739 - 771 \) \* 1000 / 1108 556 # overhead 55.6% $ expr 556 \* 11289 / 37120 \* 100 / 304 55 # relative ethernet overhead is 55% of 16450 overhead :-(. $ # Client's ethernet is WD8013EBT. $client-reading-infinite-od-output-from-ethernet time count 100000000 8.83 real 7.45 user 0.03 sys $ expr \( 883 - 758 \) \* 1000 / 883 141 # overhead 14.1% $ expr 141 \* 11289 / 37120 \* 100 / 137 30 # relative ethernet overhead is 30% of 16550 overhead :-(. Bruce
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?199510240843.SAA06640>