Date: Mon, 22 Jun 2009 09:17:05 +0900 From: Pyun YongHyeon <pyunyh@gmail.com> To: Wojciech Puchar <wojtek@wojtek.tensor.gdynia.pl> Cc: freebsd-hackers@freebsd.org Subject: Re: is RTL8139 THAT bad? Message-ID: <20090622001705.GA10712@michelle.cdnetworks.co.kr> In-Reply-To: <alpine.BSF.2.00.0906211709420.1184@wojtek.tensor.gdynia.pl> References: <alpine.BSF.2.00.0906211709420.1184@wojtek.tensor.gdynia.pl>
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On Sun, Jun 21, 2009 at 05:14:29PM +0200, Wojciech Puchar wrote: > i have pentium 200 with that card. doing ftp from other machine, getting > 3.5MB/s (HDD can 10MB/s, DMA) having 45%-55% interrupt load. > > when sending it's not that bad. > > tried writing file to disk with cat /dev/zero >file, it's only 3% ints > with 10MB/s traffic. > > > Why it's THAT bad? > Because CPU always have to copy frames to/from the controller. These CPU cycles could have been used in other task to give more performance such as SSH encryption/decryption, checksum computation etc. > 3.5MB/s is less that 2500 packets/second. 50% at 200Mhz means 100000000 > cycles spend on interrupt service, which is 40000 CPU cycles per packet. > That depends on your application. It would be ok for normal desktop PCs with fast CPU but it wouldn't be acceptable on servers that have to do lots of other processing. If you have fxp(4) or txp(4) hardwares give them try first and see what's the difference with systat(1). Pushing the hardware to the limit by sending/receiving 64 bytes frames with netperf/iperf also would be good way to see how well the controller works under extreme loads.
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