Re: [Xen-devel] Xen 4.12 release planning

[George Dunlap <dunlapg@xxxxxxxxx>]

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.

 -George

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