From: jianhai luan <jianhai.luan@oracle•com>
To: Wei Liu <wei.liu2@citrix•com>
Cc: Ian Campbell <Ian.Campbell@citrix•com>,
xen-devel@lists•xenproject.org, netdev@vger•kernel.org,
ANNIE LI <annie.li@oracle•com>
Subject: Re: DomU's network interface will hung when Dom0 running 32bit
Date: Wed, 16 Oct 2013 00:23:50 +0800 [thread overview]
Message-ID: <525D6C16.6010705@oracle.com> (raw)
In-Reply-To: <20131015160336.GT11739@zion.uk.xensource.com>
On 2013-10-16 0:03, Wei Liu wrote:
> On Tue, Oct 15, 2013 at 11:19:42PM +0800, jianhai luan wrote:
> [...]
>>>>>> * time_after_eq(now, next_credit) -> false
>>>>>> * time_before(now, expires) -> false
>>>>> If now is placed in above environment, the result will be correct
>>>>> (Sending package will be not allowed until next_credit).
>>>> No, it is not necessarily correct. Keep in mind that "now" wraps around,
>>>> which is the issue you try to fix. You still have a window to stall your
>>>> frontend.
>>> Remember that time_after_eq is supposed to work even with wraparound
>>> occurring, so long as the two times are less than MAX_LONG/2 apart.
>> Sorry for my misunderstand explanation. I mean that
>> * time_after_eq()/time_before_eq() fix the jiffies wraparound, so
>> please think about jiffies in line increasing.
>> * time_after_eq()/time_before_eq() have the range (0, MAX_LONG/2),
>> the judge will be wrong if out of the range.
>>
>> So please think about three kind environment
>> - expires now next_credit
>> --------time increases this direction ---------->
>>
>> - expires [next_credit now next_credit+MAX_LONG/2
>> --------time increase this direction ----------->
>>
>> - expires next_credit next_credit+MAX_LONG/2 now
>> --------time increadse this direction ---------->
>>
>> The first environment should be netfront consume all credit_byte
>> before next_credit, So we should pending one timer to calculator the
>> new credit_byte, and don't transmit until next_credit.
>>
>> the second environment should be calculator the credit_byte because
>> netfront don't consume all credit_byte before next_credit, and
>> time_after_eq() do correct judge.
>>
>> the third environment should be calculator in time because netfront
>> don't consume all credit_byte until next_credit.But time_after_eq do
>> error judge (time_after_eq(now, next_credit) is false), so the
>> remaining_byte isn't be increased.
>>
>> and I work on the third environment. You know now >
>> next_credit+MAX_LONG/2, time_before(now, expire) should be
>> true(time_before(now, expire) is false in first environment)
> Thanks for staighten this out for me. I'm just too dumb for this, please
> be patient with me. :-)
>
> Could you prove that time_before(now, expire) is always true in third
> case? That's where my main cencern lies. Is it because msecs_to_jiffies
> always returns MAX_JIFFY_OFFSET (which is ((LONG_MAX >> 1)-1) ) at most?
I have wrong judge in third environment. If now large than expires +
MAX_UNLONG, time_before(now, expires) will be false.
expires next_credit next_credit+MAX_UNLONG/2 expires +
MAX_UNLONG now next_credit+MAX_UNLONG
--------------------------------------------------------- time
increadse this direction ---------------------------------->
In the above environment, time_before(now, expires) will return
false. But the jiffies elapsed more time and next_credit will be
reachable in soon(time_after_eq(now, next_credit) will be true).
>
> Wei.
next prev parent reply other threads:[~2013-10-15 16:24 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-10-12 8:53 DomU's network interface will hung when Dom0 running 32bit jianhai luan
2013-10-14 11:19 ` Wei Liu
2013-10-15 2:44 ` jianhai luan
2013-10-15 8:43 ` Ian Campbell
2013-10-15 9:34 ` jianhai luan
2013-10-15 10:06 ` Wei Liu
2013-10-15 11:26 ` jianhai luan
2013-10-15 12:58 ` Wei Liu
2013-10-15 14:29 ` jianhai luan
2013-10-15 14:49 ` Wei Liu
2013-10-15 14:50 ` Ian Campbell
2013-10-15 15:19 ` jianhai luan
2013-10-15 16:03 ` Wei Liu
2013-10-15 16:23 ` jianhai luan [this message]
2013-10-16 0:15 ` jianhai luan
2013-10-16 7:35 ` jianhai luan
2013-10-16 9:39 ` [Xen-devel] " annie li
2013-10-16 13:08 ` jianhai luan
2013-10-16 13:47 ` Wei Liu
2013-10-16 15:04 ` jianhai luan
2013-10-16 15:17 ` Wei Liu
2013-10-16 16:11 ` David Vrabel
2013-10-16 16:44 ` jianhai luan
2013-10-16 15:26 ` annie li
2013-10-16 7:10 ` annie li
2013-10-16 8:46 ` Ian Campbell
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