netdev - Re: [Xen-devel] [PATCH net] xen-netback: add the scenario which now beyond the range time_after

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Message-Id: <526102DE02000078000FBFBB@nat28.tlf.novell.com>
Date:	Fri, 18 Oct 2013 08:43:58 +0100
From:	"Jan Beulich" <JBeulich@...e.com>
To:	"annie li" <annie.li@...cle.com>
Cc:	<david.vrabel@...rix.com>, <ian.campbell@...rix.com>,
	<wei.liu2@...rix.com>, <xen-devel@...ts.xenproject.org>,
	"jianhai luan" <jianhai.luan@...cle.com>, <netdev@...r.kernel.org>
Subject: Re: [Xen-devel] [PATCH net] xen-netback: add the scenario
 which now beyond the range time_after_eq().

>>> On 17.10.13 at 18:38, annie li <annie.li@...cle.com> wrote:

> On 2013-10-17 17:26, Jan Beulich wrote:
>>> Yes, the issue only can be  reproduced in 32-bit Dom0 (Beyond
>>> MAX_ULONG/2 in 64-bit will need long long time)
>>>
>>> I think the gap should be think all environment even now extending 480+.
>>> if now fall in the gap,  one timer will be pending and replenish will be
>>> in time.  Please run the attachment test program.
>> Not sure what this is supposed to tell me. I recognize that there
>> are overflow conditions not handled properly, but (a) I have a
>> hard time thinking of a sensible guest that sits idle for over 240
>> days (host uptime usually isn't even coming close to that due to
>> maintenance requirements) and (b) if there is such a sensible
>> guest, then I can't see why dealing with one being idle for over
>> 480 days should be required too.
>>
> 
> If the guest contains multiple NICs, that situation probably happens 
> when one NIC keeps idle and others work under load. BTW, how do you get 
> the 240?

2^31 / 100 / 60 / 60 / 24

Obviously with HZ=1000 the span would be smaller by a factor
of 10, which would make it even more clear that doubling the
span doesn't really help.

Jan

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