Messages in this thread | | | From | Srihari Vijayaraghavan <> | Subject | Bottleneck on /dev/null | Date | Fri, 21 Mar 2003 01:57:10 +1100 |
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Linux-2.4.latest PACKET_MMAP PCAP_FRAMES=max for tcpdump-3.8/libpcap-0.8 (from http://public.lanl.gov/cpw/) e1000 driver
2 * Xeon 2800 MHz, 512 KB L2 1 GB RAM 70 GB HW RAID-0 on SmartArray 5i 2 * 2 port Intel GigE cards (only using 1 per card for the testing purposes)
Capturing all packets and writting to /dev/null causes more packet drops than writting to hard drives (approx 40,000 packets/sec of 70 bytes for couple of minutes). I will have a comparision between those figures in a day or two, but /dev/null was well over SCSI hard drives. I thought writting (even multiple of them simultaneously) to /dev/null should be faster than fastest SCSI drives out there :) Interesting.
(And yes I see plenty of "errors", "dropped", and "overruns" in ifconfig stats on those interfaces. %system is over 80%, and tcpdump goes to "D" state many times. Simon Kirby suggested to use irq-smp_affinity to see if that helps for reducing %system time. A well optimised e1000 would definitely help as tg3 does it very well.)
I mean to test this /dev/null behavior on 2 tg3 driver configuration perhaps in couple of days time. (But the 2 tg3 cards with out-of-the-box NAPI support on 2.4.latest is able to not to loose a single packet even while writting to hard drives, then I didn't care to test it on /dev/null)
BTW I found 2.5.51 backport of e1000 NAPI support at http://havoc.gtf.org/lunz/linux/net/ Anyone knows of a recent backport or improved one for 2.4.latest (including 2.4.21-pre5 or -pre6). Patches for testing or URL is welcome.
Thanks -- Hari harisri@bigpond.com
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