Apache-Talk @lexa.ru 

Inet-Admins @info.east.ru 

Filmscanners @halftone.co.uk 

Security-alerts @yandex-team.ru 

nginx-ru @sysoev.ru 





     АРХИВ :: Inet-Admins
Inet-Admins mailing list archive (inet-admins@info.east.ru)

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [inet-admins] Fw: [gee_two@xxxxxxxxx: new SNMP vuln?]

Replying to Slawa Olhovchenkov:
> Щаззз. Где ты столько пакетов на гигабите найдешь? Там и 2М нету.

Ты прав. Облажался :((( У самого гигабита нет, ориентируюсь плохо ...


February 10/2002 -- revision 0.2:
some spell checking ;->
January 12/2002 -- revision 0.1
This is still work in progress so may change.
To keep up to date please watch this space.

Introduction to NAPI

NAPI is a proven (www.cyberus.ca/~hadi/usenix-paper.tgz) technique
to improve network performance on Linux. For more details please
read that paper.
NAPI provides a "inherent mitigation" which is bound by system capacity
as can be seen from the following data collected by Robert on Gigabit 
ethernet (e1000):

 Psize    Ipps       Tput     Rxint     Txint    Done     Ndone
   60    890000     409362        17     27622        7     6823
  128    758150     464364        21      9301       10     7738
  256    445632     774646        42     15507       21    12906
  512    232666     994445    241292     19147   241192     1062
 1024    119061    1000003    872519     19258   872511        0
 1440     85193    1000003    946576     19505   946569        0

"Ipps" stands for input packets per second. 
"Tput" == packets out of total 1M that made it out.
"txint" == transmit completion interrupts seen
"Done" == The number of times that the poll() managed to pull all
packets out of the rx ring. Note from this that the lower the
load the more we could clean up the rxring
"Ndone" == is the converse of "Done". Note again, that the higher
the load the more times we couldnt clean up the rxring.

Observe that:
when the NIC receives 890Kpackets/sec only 17 rx interrupts are generated. 
The system cant handle the processing at 1 interrupt/packet at that load level. 
At lower rates on the other hand, rx interrupts go up and therefore the
interrupt/packet ratio goes up (as observable from that table). So there is
possibility that under low enough input, you get one poll call for each
input packet caused by a single interrupt each time. And if the system 
cant handle interrupt per packet ratio of 1, then it will just have to 
chug along ....

Остальное я вырезал, там идут технические детали - многим они покажутся
неинтересными ...

Paul P 'Stingray' Komkoff 'Greatest' Jr // (icq)23200764 // (irc)Spacebar
  PPKJ1-RIPE // (smtp)i@stingr.net // (http)stingr.net // (pgp)0xA4B4ECA4

"inet-admins" Internet access mailing list. Maintained by East Connection ISP.
Mail "unsubscribe inet-admins" to Majordomo@info.east.ru if you want to quit.
Archive is accessible on http://info.east.ru/rus/inetadm.html


Copyright © Lexa Software, 1996-2009.