linux-kernel - Re: [E1000-devel] e1000 1sec latency problem

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Date:	Thu, 07 Feb 2008 09:25:03 -0800
From:	"Kok, Auke" <auke-jan.h.kok@...el.com>
To:	Max Krasnyansky <maxk@...lcomm.com>
CC:	Pavel Machek <pavel@....cz>, e1000-devel@...ts.sourceforge.net,
	jesse.brandeburg@...el.com,
	kernel list <linux-kernel@...r.kernel.org>,
	john.ronciak@...el.com, jeffrey.t.kirsher@...el.com
Subject: Re: [E1000-devel] e1000 1sec latency problem

Max Krasnyansky wrote:
> Pavel Machek wrote:
>> Hi!
>>
>> I have the famous e1000 latency problems:
>>
>> 64 bytes from 195.113.31.123: icmp_seq=68 ttl=56 time=351.9 ms
>> 64 bytes from 195.113.31.123: icmp_seq=69 ttl=56 time=209.2 ms
>> 64 bytes from 195.113.31.123: icmp_seq=70 ttl=56 time=1004.1 ms
>> 64 bytes from 195.113.31.123: icmp_seq=71 ttl=56 time=308.9 ms
>> 64 bytes from 195.113.31.123: icmp_seq=72 ttl=56 time=305.4 ms
>> 64 bytes from 195.113.31.123: icmp_seq=73 ttl=56 time=9.8 ms
>> 64 bytes from 195.113.31.123: icmp_seq=74 ttl=56 time=3.7 ms
>>
>> ...and they are still there in 2.6.25-git0. I had ethernet EEPROM
>> checksum problems, which I fixed by the update, but problems are not
>> gone.
>>
>> irqpoll helps.
>>
>> nosmp (which implies XT-PIC is being used) does not help.
>>
>>  16:       1925          0   IO-APIC-fasteoi   ahci, yenta, uhci_hcd:usb2, eth0
>>
>> Booting kernel with nosmp/ no yenta, no usb does not help.
>>
>> Hmm, as expected, interrupt load on ahci (find /) makes latencies go
>> away.
>>
>> It should be easily reproducible on x60 with latest bios, it is 100%
>> reproducible for me...
> 
> So you don't think it's related to the interrupt coalescing by any chance ?
> I'd suggest to try and disable the coalescing and see if it makes any difference.
> We've had lots of issues with coalescing misbehavior. Not this bad (ie 1 second) though.
> 
> Add this to modprobe.conf and reload e1000 module
> 
> options e1000 RxIntDelay=0,0 RxAbsIntDelay=0,0 InterruptThrottleRate=0,0 TxIntDelay=0,0 TxAbsIntDelay=0,0

that can't be the problem. irq moderation would only account for 2-3ms variance
maximum.

Pavel, can you send me the `lspci -vvv` of your machine with the very latest git
tree and after it's showing the poor ping performance?

Auke
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