Re: [Xen-devel] Xen 4.12 release planning

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 25/07/18 12:34, George Dunlap wrote:
> On Wed, Jul 25, 2018 at 12:30 PM, Andrew Cooper
> <andrew.cooper3@xxxxxxxxxx> 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.
> That diagram, however, is basically two years packed into one -- taken
> as only a single year it represents a 4-month cycle, not an 8-month
> cycle.

Oh - of course.

~Andrew

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