linux-kernel - Re: 24 lost ticks with 2.6.20.10 kernel

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <4637C313.8040002@intel.com>
Date:	Tue, 01 May 2007 15:45:39 -0700
From:	"Kok, Auke" <auke-jan.h.kok@...el.com>
To:	Chuck Ebbert <cebbert@...hat.com>
CC:	Michel Lespinasse <walken@....org>, linux-kernel@...r.kernel.org,
	Dave Jones <davej@...hat.com>, Jeb Cramer <cramerj@...el.com>,
	John Ronciak <john.ronciak@...el.com>,
	Jesse Brandeburg <jesse.brandeburg@...el.com>,
	Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Subject: Re: 24 lost ticks with 2.6.20.10 kernel

Chuck Ebbert wrote:
> Kok, Auke wrote:
>> Michel Lespinasse wrote:
>>> (I've added the E1000 maintainers to the thread as I found the issue
>>> seems to go away after I compile out that driver. For reference, I was
>>> trying to figure out why I lose exactly 24 ticks about every two
>>> seconds, as shown with report_lost_ticks. This is with a DQ965GF
>>> motherboard with onboard E1000).
>> that's perfectly likely. The main issue is that we read the hardware
>> stats every two seconds and that can consume quite some time. It's
>> strange that you are losing that many ticks IMHO, but losing one or two
>> might very well be.
>>
>> We've been playing with all sorts of solutions to this problem and
>> haven't come up with a way to reduce the load of the system reading HW
>> stats, and it remains the most likely culprit, allthough I don't rule
>> out clean routines just yet. This could very well be exaggerated at
>> 100mbit speeds as well, I never looked at that.
>>
>> I've had good results with 2.6.21.1 (even running tickless :)) on these
>> NICs. Have you tried that yet?
> 
> Maybe this could fix it in 2.6.20? (went into 2.6.21)

well, that hasn't got anything to do with stats, but is part of the clean_tx/rx 
codepath. I personally don't get any lost_ticks so I can't reproduce, but that 
was why I was hinting that you can try it for us ;)

codewise, the patch below makes our cleanup routine spend _more_ time, instead 
of less, which is why I think it's not the cause nor fix.

Auke

> 
> --------------------------------------------------------------------------
> 
> Gitweb:     http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=46fcc86dd71d70211e965102fb69414c90381880
> Commit:     46fcc86dd71d70211e965102fb69414c90381880
> Parent:     2b858bd02ffca71391161f5709588fc70da79531
> Author:     Linus Torvalds <torvalds@...dy.linux-foundation.org>
> AuthorDate: Thu Apr 19 18:21:01 2007 -0700
> Committer:  Linus Torvalds <torvalds@...dy.linux-foundation.org>
> CommitDate: Thu Apr 19 18:21:01 2007 -0700
> 
>     Revert "e1000: fix NAPI performance on 4-port adapters"
>     
>     This reverts commit 60cba200f11b6f90f35634c5cd608773ae3721b7.  It's been
>     linked to lockups of the e1000 hardware, see for example
>     
>     	https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=229603
>     
>     but it's likely that the commit itself is not really introducing the
>     bug, but just allowing an unrelated problem to rear its ugly head (ie
>     one current working theory is that the code exposes us to a hardware
>     race condition by decreasing the amount of time we spend in each NAPI
>     poll cycle).
>     
>     We'll revert it until root cause is known.  Intel has a repeatable
>     reproduction on two different machines and bus traces of the hardware
>     doing something bad.
>     
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/