[ LUGOS ] HUB kartica

[Borut Rozman]

verjetno da se moram strinjat s tabo jest mam bridge iz 3h 10mbitk :=)
imam ga itak za druge namene, switch je pa itak za boljse delo sigurno nuja,
je pa bridge alternativa...
ce pa kdo odstopi rtl8139 ke bom pa 100 mb probal !!
lp Borut

-----Original Message-----
From: jure na ponder.sou.uni-lj.si [mailto:jure na ponder.sou.uni-lj.si]On Behalf
Of Jure Koren
Sent: Thursday, January 04, 2001 11:41 AM
To: lugos-list na lugos.si
Subject: Re: [ LUGOS ] HUB kartica


On Thu, Jan 04, 2001 at 11:27:08AM +0100, Giver Root Mail wrote:
> ne vem sam mislm da mi brdige na mojmu PII300 na 450 sploh ne dvigne oz
> obremenjuje masine kaj prevec. seveda pa tud load ni kak prevelik na
masino
> ?!
> sicer pa zakaj naj nebi delala masina malo bolj kot pa je potrebno :)

Notri imas 4 rtl8139 kartice in ti ne obremenjuje 450mhz boxa
pri 100M transferih?

No, rtl8139 kartice so v tem pogledu precej slabse, kot se
mogoce sprva zdi. To sem tudi jaz poizkusil, pa se pokaze,
da je res, kar pise na zacetku driverja (rtl8139.c): masina
zgubi tla pod nogami zaradi cudne arhitekture kartice:

The receive unit uses a single linear ring buffer rather than the more
common (and more efficient) descriptor-based architecture.  Incoming frames
are sequentially stored into the Rx region, and the host copies them into
skbuffs.

Comment: While it is theoretically possible to process many frames in place,
any delay in Rx processing would cause us to drop frames.  More importantly,
the Linux protocol stack is not designed to operate in this manner.

In se transmit:

The RTL8129 uses a fixed set of four Tx descriptors in register space.
In a stunningly bad design choice, Tx frames must be 32 bit aligned.  Linux
aligns the IP header on word boundaries, and 14 byte ethernet header means
that almost all frames will need to be copied to an alignment buffer.

To se dejansko pokaze v visoki obremenitvi procesorja (ne samo pci busa)
ko je masina z rtl8139 karticami switch med dvema masinama, ki se gresta
100M full duplex in ftpjata iso image (to je bila moja testna postavitev).
PII400 je zadevo drzal na 9.8MB/s ampak se je posteno spotil. Ista
postavitev z D-linkovo kartico DFE-530TX je sla tudi do 9.9MB/s ampak
procesor ni skoraj nic pocel. Treba je se povedat da intelov
etherexpress pro 100 in compaqov turbolan nista prisla nad 9.5MB/s,
vendar procesor tudi ni prakticno nic pocel.

Skratka, kupis si 10/100M hub ki ima notri switch med 10M in 100M
segmentom. Dobis ga (5 portnega) ze za nekaj nad 30k. To je po mojem
najboljsa resitev za domaco uporabo, kjer potrebujes 100M (e.g.
peces cdje na eni masini, na drugi mas pa velik disk pa isote).

Na masini kjer imas cd rekorder ne imet rtl8139, imej etherexpress :)

--
Jure Koren                      |                       unix administrator
jure na kiss.uni-lj.si             |             gnu/Linux software developer