From: Rick Jones <rick.jones2@hp.com>
To: "John A. Sullivan III" <jsullivan@opensourcedevel.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>, netdev@vger.kernel.org
Subject: Re: Latency difference between fifo and pfifo_fast
Date: Tue, 06 Dec 2011 10:20:57 -0800 [thread overview]
Message-ID: <4EDE5D09.1060404@hp.com> (raw)
In-Reply-To: <1323161496.2448.7.camel@edumazet-HP-Compaq-6005-Pro-SFF-PC>
On 12/06/2011 12:51 AM, Eric Dumazet wrote:
> Le mardi 06 décembre 2011 à 03:39 -0500, John A. Sullivan III a écrit :
>
>>> ifconfig eth2 txqueuelen 0
>>> tc qdisc add dev eth2 root pfifo
>>> tc qdisc del dev eth2 root
>>>
>>>
>>>
>>>
>> Really? I didn't know one could do that. Thanks. However, with no
>> queue length, do I have a significant risk of dropping packets? To
>> answer your other response's question, these are Intel quad port e1000
>> cards. We are frequently pushing them to near line speed so
>> 1,000,000,000 / 1534 / 8 = 81,486 pps - John
>
> You can remove qdisc layer, since NIC itself has a TX ring queue
>
> (check exact value with ethtool -g ethX)
>
> # ethtool -g eth2
> Ring parameters for eth2:
> Pre-set maximums:
> RX: 4078
> RX Mini: 0
> RX Jumbo: 0
> TX: 4078
> Current hardware settings:
> RX: 254
> RX Mini: 0
> RX Jumbo: 0
> TX: 4078 ---- HERE ----
And while you are down at the NIC, if every microsecond is precious (no
matter how close to epsilon compared to the latencies of spinning rust
:) you might consider disabling interrupt coalescing via ethtool -C.
rick jones
next prev parent reply other threads:[~2011-12-06 18:21 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <8f05fdb0-6e4c-4adf-b8d1-bd67a0dc114f@jasiiieee>
2011-12-06 4:10 ` Latency difference between fifo and pfifo_fast John A. Sullivan III
2011-12-06 6:02 ` Eric Dumazet
2011-12-06 6:29 ` Eric Dumazet
2011-12-06 8:39 ` John A. Sullivan III
2011-12-06 8:51 ` Eric Dumazet
2011-12-06 18:20 ` Rick Jones [this message]
2011-12-06 18:39 ` Dave Taht
2011-12-06 19:44 ` John A. Sullivan III
2011-12-07 13:04 ` Eric Dumazet
2011-12-07 13:27 ` Dave Taht
2011-12-07 14:08 ` David Laight
2011-12-08 0:05 ` John A. Sullivan III
2011-12-07 23:27 ` Stephen Hemminger
2011-12-08 0:34 ` John A. Sullivan III
2011-12-07 23:49 ` Stephen Hemminger
2011-12-08 3:20 ` John A. Sullivan III
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