Re: [Xen-devel] Xen 4.12 release planning

[Juergen Gross <jgross@xxxxxxxx>]

On 25/07/18 13:30, Andrew Cooper wrote:
> On 25/07/18 12:24, George Dunlap wrote:
>> On Wed, Jul 25, 2018 at 10:22 AM, Juergen Gross <jgross@xxxxxxxx> wrote:
>>> On 25/07/18 10:19, Andrew Cooper wrote:
>>>> On 25/07/2018 09:15, Julien Grall wrote:
>>>>> Hi Juergen,
>>>>>
>>>>> On 25/07/18 08:19, Juergen Gross wrote:
>>>>>> Its time to plan the Xen 4.12 release dates.
>>>>>>
>>>>>> There have been concerns with the schedule of 6 months between releases,
>>>>>> as this scheme is leading to too many supported versions of Xen at a
>>>>>> time. The needed resources to backport bug fixes and security fixes as
>>>>>> well as doing the tests for all those releases are a limiting factor to
>>>>>> push out the current main release as well as point releases on time.
>>>>>>
>>>>>> After some discussions at the Xen developer summit, on xen-devel and
>>>>>> between the committers a slightly longer release cycle of 8 or 9 months
>>>>>> was suggested.
>>>>>>
>>>>>> With 18 months of full support and 36 months of security support the
>>>>>> number of concurrent supported releases will be the same with either 8
>>>>>> or 9 months release cycles, so I have chosen an 8 month cycle for now.
>>>>>> Having only 3 possible times in the year for a release will make it
>>>>>> easier to avoid major holiday seasons. >
>>>>>> In case there is no objection I'm planning Xen 4.12 with:
>>>>>>
>>>>>> * Last posting date: December 14th, 2018
>>>>>> * Hard code freeze: January 11th, 2019
>>>>> In general, you would expect western people to slow down during
>>>>> Christmas period and have to deal with a pile of e-mail just after New
>>>>> Year. So I think, this is not very convenient period for a code freeze.
>>>>>
>>>>> I usually take more holidays around Christmas and New Year. For this
>>>>> year, I will be on holidays from 21st December until the 13th January.
>>>>> This basically means my cut off for Arm patches will be 21st December
>>>>> or potentially few days before to avoid having the likely last minute
>>>>> rush.
>>>> Given that we have decided to switch to a difference cadence, it would
>>>> be prudent to work out when the best alignment of an 8-month cadence
>>>> would be, rather than having it 8 months from now.  If that means a
>>>> one-off shorter or longer cycle for 4.12 then so be it.
>>> The general holiday seasons are:
>>>
>>> - Chinese new year (end of January ... mid of February), 2 weeks
>>> - Eastern (end of March ... end of April), only a weak dependency?
>>> - summer (August?), second half of July and first half of September as
>>>   a weak dependency
>>> - Christmas (end of December ... start of January), adding one week as
>>>   a weak dependency
>>>
>>> We don't like the planned release to be in or just before a holiday
>>> season. The period between last posting date and freeze should last
>>> 2 weeks, the freeze period should last 6 weeks.
>>>
>>> In the diagram below I have used a 'X' for a major holiday season and
>>> a 'x' for a weak dependency. The lines below are possible release date
>>> variants just shifted by a weak each to show all possibilities.
>>>
>>> Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
>>> Xx.XXXXX...xxxx...........xxXXXXx..............X      holidays
>>> ffFFFFFFR.......ffFFFFFFR.......ffFFFFFFR.......
>>> .ffFFFFFFR.......ffFFFFFFR.......ffFFFFFFR......
>>> ..ffFFFFFFR.......ffFFFFFFR.......ffFFFFFFR.....
>>> ...ffFFFFFFR.......ffFFFFFFR.......ffFFFFFFR....
>>> ....ffFFFFFFR.......ffFFFFFFR.......ffFFFFFFR...
>>> .....ffFFFFFFR.......ffFFFFFFR.......ffFFFFFFR..
>>> ......ffFFFFFFR.......ffFFFFFFR.......ffFFFFFFR.
>>> .......ffFFFFFFR.......ffFFFFFFR.......ffFFFFFFR
>>> R.......ffFFFFFFR.......ffFFFFFFR.......ffFFFFFF
>>> FR.......ffFFFFFFR.......ffFFFFFFR.......ffFFFFF
>>> FFR.......ffFFFFFFR.......ffFFFFFFR.......ffFFFF
>>> FFFR.......ffFFFFFFR.......ffFFFFFFR.......ffFFF
>>> FFFFR.......ffFFFFFFR.......ffFFFFFFR.......ffFF
>>> FFFFFR.......ffFFFFFFR.......ffFFFFFFR.......ffF
>>> FFFFFFR.......ffFFFFFFR.......ffFFFFFFR.......ff
>>> fFFFFFFR.......ffFFFFFFR.......ffFFFFFFR.......f
>>>
>>> We can rule out several variants with release dates just before or in a
>>> holiday season:
>>>
>>> Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
>>> Xx.XXXXX...xxxx...........xxXXXXx..............X      holidays
>>> ffFFFFFFR.......ffFFFFFFR.......ffFFFFFFR.......
>>> .ffFFFFFFR.......ffFFFFFFR.......ffFFFFFFR......
>>>
>>> Best fit seems to be releasing in first half of March/July/November. The
>>> main clash seems to be Chinese new year in the freeze period, but
>>> avoiding that would mean we'd have to either move into Christmas or
>>> Eastern, or to use a schedule with varying periods.
>>>
>>> Please remember that Chinese new year is only 2 weeks long (at varying
>>> dates) so only 2 weeks of the freeze period are hit. Next year the
>>> Chinese new year will be at February 5th.
>>>
>>> For my 4.12 plan I've added some extra weeks between last posting date
>>> and release date to accommodate for the holiday seasons, resulting in
>>> my suggestion.
>> Thanks for the detailed analysis Juregen.  This seems good to me.
> 
> I think it is also worth staying that we need to work on reducing the
> length of the hard freeze date, because as is visible from that diagram,
> its basically half the year.

No, it isn't. It can happen half the year, but in reality it is only
every 9 months (so in one case out of three).

I believe that question is orthogonal to the one about time between
releases. It basically boils down to the question when to branch the new
release off the main trunk.


Juergen


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