Notice of plan to deprecate map zone file format

[Timothe Litt]

I'm not a consumer of this and agree that it's up to users to speak up,
so I'll stop here - with one final observation.

The issue comment containing the benchmarks includes:

> Speedup provided by the |map| format does not seem significant enough
> to warrant the complexity of map format, especially when we take into
> account that the difference measured in terms of "real time" is in
> order of 10s of seconds.
10s of seconds *per zone* can certainly add up.  Call it 10 secs/zone *
100,000 zones = 1M sec / 3600 = 278 hrs *saved*.

Suppose loading zones is not disk limited, and cores scale linearly
(e.g. no lock conflicts & an index lets each core find a zone to work on
for free).  So give it 16 cores (each taking on one complete zone), and
it's still 17 hrs saved.  Real life won't be that efficient - meaning
cores won't help that much.

A new memory mapped data structure that didn't require "updating node
pointers" (e.g. that used offsets instead of pointers) may be worth
considering.  In current hardware and with a decent compiler and coding,
the apparent cost of this over absolute pointers may well be vanishingly
small.

OK, that was two.

Timothe Litt
ACM Distinguished Engineer
--------------------------
This communication may not represent the ACM or my employer's views,
if any, on the matters discussed. 

On 10-Sep-21 12:56, Victoria Risk wrote:
>
>>>> After all the "other improvements in performance" that you cited,
>>>> what is the performance difference between map and the other formats?
>>>
>>> I don’t know that, to be honest. We don’t have the resources to
>>> benchmark everything. Maybe someone on this list could?  We would
>>> also like to be able to embark on a wholesale update to the rbtdb
>>> next year and this is the sort of thing that might complicate
>>> refactoring unnecessarily.
>
>
> I was wrong, and in fact we have benchmarked it.
> See https://gitlab.isc.org/isc-projects/bind9/-/issues/2882
> <https://gitlab.isc.org/isc-projects/bind9/-/issues/2882> for details.
> Map format is still faster than raw, but not so much faster that it
> warrants retaining it, given it is riskier, harder to maintain and we
> have no feedback from users that it is important to them.  It also
> seems not to work with large numbers of zones, (>100K) at least in
> current versions of 9.11 and 9.16, which is further indication that it
> isn’t in wide use or we would have had complaints. 
>
> We also have discussed internally that there are other factors, other
> than loading the zone files, that may have more impact on the time it
> takes a BIND server to restart.
>
> If anyone out there is using it successfully, and wants us to keep
> this feature, this would be the time to speak up!
>
> Thank you,
>
> Vicky
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